Ghostty supports OSC 9;4

[adamchalmers]

This enables the new in-terminal progress bar (which uses OSC 9;4) if nextest is running inside the Ghostty terminal.

See #2715

Here's a video of it working, with my local nextest build.

Nextest.with.progress.bar.mp4

It also does a tiny incidental refactor, making the other terminal-specific checks use var_os instead of var to use fewer allocations.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.89%. Comparing base (36843fd) to head (e971c43).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
nextest-runner/src/reporter/displayer/progress.rs	0.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2724      +/-   ##
==========================================
- Coverage   77.91%   77.89%   -0.02%     
==========================================
  Files         112      112              
  Lines       25692    25696       +4     
==========================================
- Hits        20017    20016       -1     
- Misses       5675     5680       +5     

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[RGBCube]

awesome :) though it would be really nice if there was an universally established protocol to query supported emulator features, too late for that :(

[sunshowers]

Thanks!