chore(quality): exclude test/fixtures from CodeQL, ESLint, and Prettier (#1313)

Test fixtures are intentionally synthetic inputs (broken/unused code,
malformed samples) used to exercise the analyzer. Quality-tool findings
on them are noise, not real bugs — they were drowning out actionable
signal in the GitHub Security tab.

- CodeQL: add `**/test/fixtures/**` to paths-ignore in codeql.yml
- ESLint: add `gitnexus-web/test/fixtures/**` to global ignores
  (the gitnexus/ counterpart was already ignored)
- Prettier: add `gitnexus-web/test/fixtures/` to .prettierignore
  (same gap as ESLint)

Real test files (*.test.ts) remain in scope so genuine issues like
js/file-system-race and js/insecure-temporary-file in test code still
surface.

.github/workflows/codeql.yml

@@ -60,6 +60,10 @@ jobs:
               - 'gitnexus/vendor/**'
               - 'gitnexus/src/core/parsing/**/parser.c'
               - 'gitnexus/src/core/parsing/**/parser.js'
+              # Test fixtures are intentionally synthetic inputs (broken/unused
+              # code, malformed samples) used to exercise the analyzer. CodeQL
+              # findings here are noise, not real bugs.
+              - '**/test/fixtures/**'
 
       - name: Perform CodeQL Analysis
         uses: github/codeql-action/analyze@0daab03d71ff584ef619d027a3fd9146679c5d84 # v3.35.3

.prettierignore

@@ -2,6 +2,7 @@ dist/
 coverage/
 gitnexus/vendor/
 gitnexus/test/fixtures/
+gitnexus-web/test/fixtures/
 gitnexus-web/playwright-report/
 gitnexus-web/test-results/
 *.d.ts

eslint.config.mjs

@@ -14,6 +14,7 @@ export default [
       'gitnexus/vendor/**',
       'gitnexus-web/src/vendor/**',
       'gitnexus/test/fixtures/**',
+      'gitnexus-web/test/fixtures/**',
       'gitnexus-web/playwright-report/**',
       'gitnexus-web/test-results/**',
       '**/*.d.ts',