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/observability/event.test.cjs

@@ -7,7 +7,7 @@
  * observable behaviour (return values). No mocks, no vacuous truths.
  */
 
-const { describe, test, beforeEach, afterEach } = require('node:test');
+const { describe, test } = require('node:test');
 const assert = require('node:assert/strict');
 
 const {

tests/observability/hub-logger-integration.test.cjs

@@ -22,12 +22,10 @@ const os = require('os');
 
 const {
   createHub,
-  ERROR_KINDS,
 } = require('../../gsd-core/bin/lib/command-routing-hub.cjs');
 
 const {
   createDefaultLogger,
-  createNoOpLogger,
 } = require('../../gsd-core/bin/lib/observability/logger.cjs');
 const { cleanup } = require('../helpers.cjs');