After seeing that he has not posted it here yet, I'll do it instead. This is a master list of bugs, crashes and possible features/improvements that ccapitalK found during the attempt at doing Advent of Code 2021 entirely in Serenity. Feel free to break these out into their own issues if need be + reference them back to here so we can keep this checklist up-to-date. List taken from here

• Render hard tabs in HS: This is needed since makefiles use hard tabs and are commonly edited in hack studio. The actual rendering needs to be done in the text editor widget, and we might also want make it toggle-able whether we want to automatically expand tabs to spaces or not.
• [Feature] Ctrl+Tab shift through recent files in HS: This is something that comes up due to muscle memory, I think having multiple tabs for open files would be nice too.
• Queue commands in HS (Ctrl+B -> Ctrl+R): Basically, if you hit Ctrl+B then Ctrl+R before the build has completed, HS complains that there is a command still executing. It would be nice if it instead queued the run action. (I think for this case, providing a Build and Execute command might also suffice).
• Spice agent doesn't work: I tried setting up spice and wasn't able to do it, might have been me messing up but I think that since we have support for it in the code, we might as well have a look into improving the experience of getting it running (copy paste between host and guest is super useful). If Spice is working fine and it was just me failing to configure it, it might be a good idea to get some instructions up for setting it up.
• Fix weird error messages for ssh (Invalid line seperator or something): There are two bugs here. The first one was fixed, where ssh kept dying when used by git to connect to an unknown host (fixed by #11238 ). The second one happens sometimes when git tries to use ssh but can't authenticate properly, what happens is it ends up exiting with an error message about invalid line separators because it parses the plain text response that github ends up sending back. I believe this isn't the behaviour on other unix systems, so there may be a bug here.
• Icon for Makefiles
• [No Repro] Fatal Error: The input '/tmp/SOMETHING.s' and output 'main.o' files are the same
• [Difficult Repro] HS crashed when debugging crash
• HackStudio doesn't enable all the cool header shit because that's done through Serenity's CMake config
  • E.G. outln() compile time format check doesn't work
• [Feature] Add clang-format on save if available
• Hack Studio should remember where the last project was created if it hasn't been closed since then (during the new project wizard)
  • [Feature] Make configuration option for number of lines of overscroll to bring into view when writing with cursor off screen
• Crash in HS:

   	7634.597 HackStudio(53:53): ASSERTION FAILED: m_history_start == 0                                                                                                         
   	./Userland/Libraries/LibVT/Terminal.h:392                                                                                                                                  
   	7634.597 [#0 HackStudio(53:53)]: Terminating HackStudio(53) due to signal 6                                                                                                
   	7634.597 [#0 FinalizerTask(4:4)]: 0xdeadc0de  Kernel::Processor::switch_context(Kernel::Thread*&, Kernel::Thread*&) + 0x572                                                                                            
   	0xdeadc0de  Kernel::Scheduler::context_switch(Kernel::Thread*) [clone .localalias] + 0x40e                                                                                 
   	0xdeadc0de  Kernel::Scheduler::pick_next() [clone .localalias] + 0x12f                                                                                                     
   	0xdeadc0de  Kernel::Processor::check_invoke_scheduler() [clone .localalias] + 0x214                                                                                        
   	0xdeadc0de  Kernel::Thread::die_if_needed() [clone .localalias] + 0x1bb                                                                                                    
   	0xdeadc0de  syscall_handler + 0x2370                                                                                                                                       
   	0xdeadc0de  syscall_asm_entry + 0x31                                                                                                                                       
   	0x4d7d53e5  libc.so: .text + 0x163e5                                                                                                                                       
   	0x4d7c098a  libc.so: .text + 0x198a                                                                                                                                        
   	0x4d7c141d  libc.so: .text + 0x241d                                                                                                                                        
   	0x94c07ebe  libvt.so.serenity: .text + 0x7ebe                                                                                                                              
   	0x94c08521  libvt.so.serenity: .text + 0x8521                                                                                                                              
   	0x94c08619  libvt.so.serenity: .text + 0x8619                                                                                                                              
   	0x94c19fe0  libvt.so.serenity: .text + 0x19fe0                                                                                                                             
   	0x94c0b8ea  libvt.so.serenity: .text + 0xb8ea                                                                                                                              
   	0x94c07464  libvt.so.serenity: .text + 0x7464                                                                                                                              
   	0x94c1023f  libvt.so.serenity: .text + 0x1023f                                                                                                                             
   	0x1da7548a  libcore.so.serenity: .text + 0x2b48a                                                                                                                           
   	0x1da76781  libcore.so.serenity: .text + 0x2c781                                                                                                                           
   	0x1da617f1  libcore.so.serenity: .text + 0x177f1                                                                                                                           
   	0x1da6233b  libcore.so.serenity: .text + 0x1833b                                                                                                                           
   	0x3bdb4788  libgui.so.serenity: .text + 0x20788                                                                                                                            
   	0x5f0a22bd  /bin/HackStudio: .text + 0x682bd                                                                                                                               
   	0x404eb1c2  libmain.so.serenity: .text + 0x1c2                                       
   	0x5f03c1fd  /bin/HackStudio: .text + 0x21fd                                                                                                                                
   	                                                                                                                                                                           
   	7634.606 [#0 FinalizerTask(4:4)]: Generating coredump for pid: 53                                                                                                          
   	7634.892 CrashDaemon(16:16): New coredump file: /tmp/coredump/HackStudio_53_1638617948                                                                                     
   	7634.912 [#0 g++(711:711)]: Terminating g++(711) due to signal 1                                                                                                           
   	7636.512 CrashReporter(712:712): Generating backtrace took 1507 ms                                                                                                         
   	7636.512 CrashReporter(712:712): --- Backtrace for thread #0 (TID 53) ---                                                                                                  
   	7636.512 CrashReporter(712:712): 0x6258902e: [libsystem.so] syscall2 +0xe (syscall.cpp:25 => syscall.cpp:24)                                                               
   	7636.512 CrashReporter(712:712): 0x4d7d53e4: [libc.so] raise +0x24 (syscall.h:35 => signal.cpp:21 => signal.cpp:34)                                                        
   	7636.512 CrashReporter(712:712): 0x4d7c0989: [libc.so] abort +0x29 (stdlib.cpp:215)                                                                                        
   	7636.516 CrashReporter(712:712): 0x4d7c141c: [libc.so] __assertion_failed +0x6c (assert.cpp:33)                                                                            
   	7636.516 CrashReporter(712:712): 0x94c07ebd: [libvt.so.serenity] VT::Terminal::scroll_up(unsigned short, unsigned short, unsigned long) [clone .localalias] +0x5ed (Terminal.h:392 => Terminal.cpp:783)
   	7636.516 CrashReporter(712:712): 0x94c08520: [libvt.so.serenity] VT::Terminal::linefeed() [clone .localalias] +0xe0 (Terminal.cpp:756 => Terminal.cpp:738)                                                             
   	7636.516 CrashReporter(712:712): 0x94c08618: [libvt.so.serenity] .L1818 +0x48 (Terminal.cpp:1055)                                                                                             
   	7636.516 CrashReporter(712:712): 0x94c19fdf: [libvt.so.serenity] .L191 +0xf (EscapeSequenceParser.cpp:58)                                                                                     
   	7636.516 CrashReporter(712:712): 0x94c0b8e9: [libvt.so.serenity] AK::Function<void (VT::EscapeSequenceStateMachine::Action, unsigned char)>::operator()(VT::EscapeSequenceStateMachine::Action, unsigned char) const +0x69 (Function.h:91)
   	7636.516 CrashReporter(712:712): 0x94c07463: [libvt.so.serenity] .L1339 +0x33 (EscapeSequenceStateMachine.h:81 => EscapeSequenceParser.h:45 => Terminal.cpp:996)
   	7636.516 CrashReporter(712:712): 0x94c1023e: [libvt.so.serenity] VT::TerminalWidget::set_pty_master_fd(int)::{lambda()#1}::operator()() const +0x8e (TerminalWidget.cpp:72)                                            
   	7636.521 CrashReporter(712:712): 0x1da75489: [libcore.so.serenity] Core::Notifier::event(Core::Event&) +0x99 (Function.h:91)
   	7636.521 CrashReporter(712:712): 0x1da76780: [libcore.so.serenity] Core::Object::dispatch_event(Core::Event&, Core::Object*) +0xb0 (Object.cpp:219)
   	7636.521 CrashReporter(712:712): 0x1da617f0: [libcore.so.serenity] Core::EventLoop::pump(Core::EventLoop::WaitMode) +0x180 (EventLoop.cpp:413)
   	7636.521 CrashReporter(712:712): 0x1da6233a: [libcore.so.serenity] Core::EventLoop::exec() +0x6a (EventLoop.cpp:370)
   	7636.521 CrashReporter(712:712): 0x3bdb4787: [libgui.so.serenity] GUI::Application::exec() +0x27 (Application.cpp:119)
   	7636.521 CrashReporter(712:712): 0x5f0a22bc: [/bin/HackStudio] serenity_main(Main::Arguments) +0x96c (main.cpp:85)
   	7636.521 CrashReporter(712:712): 0x404eb1c1: [libmain.so.serenity] main +0x81 (Main.cpp:24)
   	7636.521 CrashReporter(712:712): 0x5f03c1fc: [/bin/HackStudio] _entry +0x5c (crt0.cpp:46)
   	7636.598 CrashReporter(712:712): perror(): unveil: Operation not permitted
   	7636.600 [#0 FinalizerTask(4:4)]: Process 'CrashReporter' exited with the veil left open

• [Feature] Recent projects menu in Hack Studio
• Ctrl+P Crashes Hack studio?
• [Optimization] The runner window could be a little more snappy
• [Hard Repro] I once saw part of the command output be printed beyond the (Command exited with 0) line in HS Command Output
• [Feature] Maybe Build and Output tabs should be separate in HS?
• [Feature] Open project on selected folder in top left dir browser
• We have a syscall called dump_backtrace which currently does not work, the functionality provided by it would be really useful. We should either repair the syscall, or remove it if it is no longer workable.

cc @ccapitalK