fix(server): reduce editor scan work and retain partial results

[CodeZeno]

What Changed

Reuse PATH directory listings during editor discovery to reduce repeated filesystem checks. Return and cache editors found within four seconds if the scan takes longer. Preserve filesystem case-sensitivity behaviour and add tests for directory caching, fallback checks, and partial results.

Why

T3 Code on my Windows 11 machine would show an empty 'Open' list as it would timeout while looking for available editors. Even if some were found, they were thrown out if it reached the timeout.
The reason was 29,568 file checks being performed (22 commands (editors), 56 paths (my windows PATH), 12 file extensions and 2 case checks)

UI Changes

Before:

After:

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for any UI changes

Summary by CodeRabbit

• Bug Fixes

  • Editor discovery now returns successfully detected editors even when another probe stalls or times out.
  • Completed discovery results remain available for subsequent requests.
  • Command lookup is more reliable on case-sensitive file systems and safely falls back when directory contents cannot be read.

• Performance

  • Repeated command lookups within the same operation reuse directory information, reducing unnecessary file-system checks while preserving PATH priority.

[macroscopeapp]

Approvability

Verdict: Approved at 9cbe171

Macroscope's review found this PR approvable — The PR makes a focused correction to existing editor discovery: it reuses PATH listings and preserves editors found before a slow probe times out. Runtime changes are confined to this discovery path, with fallback behavior and partial-result caching covered by targeted tests.

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 9cbe17114685f839dd79edca10ece8ca25de97c0 and 1be2536.

📒 Files selected for processing (4)

• apps/server/src/process/externalLauncher.test.ts
• apps/server/src/process/externalLauncher.ts
• packages/shared/src/shell.test.ts
• packages/shared/src/shell.ts

Included review availability: Your plan provides up to 10 included reviews per hour; 9 remain after this review.

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📝 Walkthrough

Walkthrough

Changes

The shell resolver now caches PATH directory listings and handles listing errors. Editor discovery now returns and caches completed probes after a four-second timeout.

Command discovery and editor probing

Layer / File(s)	Summary
Cached PATH directory resolution packages/shared/src/shell.ts, packages/shared/src/shell.test.ts	Command resolution caches directory listings, applies platform-specific case handling, and falls back to file probes for non-NotFound errors.
Bounded editor discovery apps/server/src/process/externalLauncher.ts, apps/server/src/process/externalLauncher.test.ts	Editor discovery now times out after four seconds and caches completed probes. Tests cover timeout recovery and memoization.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

Suggested reviewers: juliusmarminge, utkarshusername

Merge Risk: ⚪ Minimal · up to 1be25

Completed editor discoveries remain available when a later probe times out, with no confirmed merge-blocking risk.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 4 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the primary changes: reducing editor scan work and retaining partial results during timeouts.
Description check	✅ Passed	The description includes the required What Changed, Why, UI Changes, and Checklist sections. It explains the problem, solution, testing scope, and provides before-and-after screenshots for the UI chan…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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