chore(scan,dsn): trim session cruft from comment-heavy files

[BYK]

Summary

Cleanup pass over the scan/ and dsn/ modules after the grep + worker-pool stack (#791, #804, #805, #807, #797) landed. Removed comment bloat accumulated across the 6+ review cycles those PRs went through — redundant bug-history narration, repeated explanations of ref/unref boolean semantics, "pre-PR-N" references, and other scars that wouldn't survive a fresh-eyes read.

Net −708 LOC across 12 files. No behavior changes.

Per-file reductions

File	Before	After	Δ
src/lib/scan/worker-pool.ts	466	312	−33%
src/lib/scan/grep.ts	985	712	−28%
src/lib/dsn/code-scanner.ts	541	377	−30%
src/lib/scan/grep-worker.js	153	114	−25%
src/lib/dsn/scan-options.ts	70	52	−26%
src/lib/init/tools/grep.ts	122	98	−20%
src/lib/init/tools/glob.ts	74	59	−20%

Plus minor trims in types.ts, walker.ts, path-utils.ts, scan/glob.ts, and script/text-import-plugin.ts.

What was removed

• Redundant explanations of Worker.ref() / .unref() boolean semantics (stated 3× in worker-pool.ts — kept once, on the primary ref/unref helper pair).
• Multi-paragraph "earlier iteration did X, deadlocked, so we now do Y" histories — kept in git log where they belong.
• "pre-PR-3" / "pre-refactor" / "previous version" narration that explained how code used to look before the current session's work.
• File-header docstrings that repeated what the module structure and exports already told you.
• Rationale comments for biome-ignores that were already justified by adjacent context.

What was kept

• Every biome-ignore comment (all still justified).
• Every "why" comment tied to a real gotcha (e.g., the length-change warning on case-insensitive literal prefilters, the /g flag cloning rationale, the pipeline-failure detector explanation).
• Every JSDoc on exported functions and types.
• All inline comments that explain non-obvious constraints (sandbox enforcement, cache-contract stability, etc.).

Test plan

• bunx tsc --noEmit — clean
• bun run lint — clean (1 pre-existing markdown warning)
• bun test --timeout 15000 test/lib test/commands test/types — 5641 pass, 0 fail
• bun test test/isolated — 138 pass
• bun run bench --size large --runs 3 — no perf regression (scan.grepFiles 167ms, scanCodeForDsns 232ms — matching pre-trim numbers)
• bun run build --single — binary builds and exits cleanly on sentry project view from empty dir (3 consecutive runs, all exit=1)

🤖 Generated with Claude Code

Co-authored-by: Claude Opus 4.7 (1M context) noreply@anthropic.com

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Codecov Results 📊

✅ 138 passed | Total: 138 | Pass Rate: 100% | Execution Time: 0ms

📊 Comparison with Base Branch

Metric	Change
Total Tests	—
Passed Tests	—
Failed Tests	—
Skipped Tests	—

✨ No test changes detected

All tests are passing successfully.

❌ Patch coverage is 27.78%. Project has 1943 uncovered lines.
✅ Project coverage is 95.21%. Comparing base (base) to head (head).

Files with missing lines (2)

File	Patch %	Lines
src/lib/scan/grep.ts	0.00%	⚠️ 12 Missing
src/lib/scan/worker-pool.ts	66.67%	⚠️ 1 Missing

Coverage diff

@@            Coverage Diff             @@
##          main       #PR       +/-##
==========================================
+ Coverage    95.04%    95.21%    +0.17%
==========================================
  Files          282       282         —
  Lines        40661     40577       -84
  Branches         0         0         —
==========================================
+ Hits         38646     38634       -12
- Misses        2015      1943       -72
- Partials         0         0         —

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