refactor(scripts): organize into build/dev/check/docs/i18n/ad-hoc subfolders

Reorganizes the 29 active scripts under scripts/ into purpose-driven
subfolders:

- scripts/build/    (11) — Build, install, publish, runtime env
- scripts/dev/      (13) — Dev servers, test runners, healthchecks
- scripts/check/    (10) — Lint/validation/coverage checks
- scripts/docs/      (2) — Docs index and provider reference generation
- scripts/i18n/     (+3) — Adds Python translation utilities (check/validate/autotranslate)
- scripts/ad-hoc/    (4) — One-shot maintenance utilities

Updates all references in package.json, electron/package.json,
.husky/pre-commit, .github/workflows/ci.yml, Dockerfile, src/,
tests/, scripts/ internal cross-imports, playwright.config.ts,
and English docs (CODEBASE_DOCUMENTATION, ENVIRONMENT, FEATURES,
RELEASE_CHECKLIST, COVERAGE_PLAN, ELECTRON_GUIDE, I18N, GEMINI).

Also patches scripts/build/pack-artifact-policy.ts so the npm pack
allowlist mirrors the new layout.

Validates with:
- npm run lint            (exit 0 — pre-existing minified-bundle errors only)
- npm run typecheck:core  (exit 0)
- npm run check:docs-all  (exit 0)
- unit tests for moved scripts (57 tests pass)

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

.github/workflows/ci.yml

@@ -71,7 +71,7 @@ jobs:
 
       - name: Validate ${{ matrix.lang }}
         run: |
-          python3 scripts/validate_translation.py quick -l '${{ matrix.lang }}' > result.txt
+          python3 scripts/i18n/validate_translation.py quick -l '${{ matrix.lang }}' > result.txt
 
       - name: Upload result
         if: always()
@@ -94,7 +94,7 @@ jobs:
       - name: Fetch base branch
         run: git fetch --no-tags origin "${GITHUB_BASE_REF}" --depth=1
       - name: Validate source changes include tests
-        run: node scripts/check-pr-test-policy.mjs --summary-file .artifacts/pr-test-policy.md
+        run: node scripts/check/check-pr-test-policy.mjs --summary-file .artifacts/pr-test-policy.md
       - name: Publish PR test policy summary
         if: always()
         run: |
@@ -255,7 +255,7 @@ jobs:
         run: |
           mkdir -p coverage
           if [ -f coverage/coverage-summary.json ]; then
-            node scripts/test-report-summary.mjs \
+            node scripts/check/test-report-summary.mjs \
               --input coverage/coverage-summary.json \
               --output coverage/coverage-report.md \
               --threshold 60