chore(scan,dsn): trim session cruft from comment-heavy files (#810)

## 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-ignore`s 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

- [x] `bunx tsc --noEmit` — clean
- [x] `bun run lint` — clean (1 pre-existing markdown warning)
- [x] `bun test --timeout 15000 test/lib test/commands test/types` —
**5641 pass, 0 fail**
- [x] `bun test test/isolated` — 138 pass
- [x] `bun run bench --size large --runs 3` — no perf regression
(`scan.grepFiles` 167ms, `scanCodeForDsns` 232ms — matching pre-trim
numbers)
- [x] `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](https://claude.com/claude-code)

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

Author: BYK

script/text-import-plugin.ts

@@ -1,31 +1,20 @@
 /**
  * esbuild plugin that polyfills Bun's `with { type: "text" }` import
- * attribute.
+ * attribute (esbuild only supports `json`). Intercepts matching
+ * imports, reads the file, and default-exports its contents as a
+ * string. Runtime behavior matches Bun's native handling.
  *
- * esbuild doesn't natively support the `text` import attribute (only
- * `json`), but Bun does. Our CLI code uses it to load the grep worker
- * source as a string at bundle time (see
- * `src/lib/scan/worker-pool.ts`). Without this plugin, esbuild errors
- * with `Importing with a type attribute of "text" is not supported`
- * on any file that imports a sibling `.js` as text.
- *
- * The plugin intercepts imports whose `with` attribute matches
- * `{ type: "text" }`, reads the file from disk, and emits it as a JS
- * module that default-exports the file's contents as a string.
- * Runtime behavior matches Bun's native handling, so the same source
- * works in dev (via `bun run`) and in compiled binaries (esbuild +
- * `bun build --compile` two-step).
- *
- * Used by both `script/build.ts` (single-file executable) and
- * `script/bundle.ts` (CJS library bundle for npm).
+ * Used by `script/build.ts` (single-file executable) and
+ * `script/bundle.ts` (CJS library bundle) so the grep-worker source
+ * in `src/lib/scan/worker-pool.ts` loads correctly in both dev and
+ * compiled builds.
  */
 
 import { readFileSync } from "node:fs";
 import { resolve as resolvePath } from "node:path";
 import type { Plugin } from "esbuild";
 
 const TEXT_IMPORT_NS = "text-import";
-/** Match-any filter for esbuild's plugin API. Hoisted for top-level-regex lint. */
 const ANY_FILTER = /.*/;
 
 export const textImportPlugin: Plugin = {