chore: clean up clear-cut ESLint warnings (#732) (#734)

Pay down pre-existing error→warn lint debt. Removes dead imports/vars, unused functions, redundant regex/string escapes, and stale eslint-disable directives; converts unused `catch (_e)` to optional catch binding (src/*.cts).

No behavior change. Lint 345→125 warnings (0 errors); deferred categories (n/no-process-exit, test-sleeps, control-regex) tracked in #732 for follow-up. Full test suite green (0 failures); code-review verified all removals unused and all escape fixes semantics-preserving.

Closes #732

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

tests/code-review-command.test.cjs

@@ -10,7 +10,7 @@
  * wired into config, templates, and the ship workflow.
  */
 
-const { describe, test, beforeEach, afterEach } = require('node:test');
+const { describe, test } = require('node:test');
 const assert = require('node:assert/strict');
 const fs = require('fs');
 const path = require('path');