CI quality uplift: ESLint + Vitest + coverage gating + small extras (#161)

[rpgmem]

Closes #161.

Summary

Four commits implementing the CI quality uplift from #161. Each is independently revertable.

Sprint	Commit	What
S1	5df4472	ESLint 9 flat config + lint:js script + new Lint workflow. Fixed 3 real bugs surfaced by the first pass.
S2	2727b57	Vitest + jsdom infrastructure + 23 unit tests covering validateDateTime, pickHideMode, analyzeDateTimeOrder. Test surfaced and fixed a real bug (JS analyzeDateTimeOrder wasn't defaulting time_mode to 'daily' like the PHP mirror does).
S3	e6da643	Coverage job loses continue-on-error: true and gains a floor enforcer that parses clover XML and writes a step-summary table. Floor set to 50% — under the baseline so day-one PRs aren't blocked, high enough to catch a regression.
S4-extras	38d487a	composer validate --strict in the audit job; new Stylelint on assets/css job (was an unused npm script); new CodeQL workflow with javascript + php matrix on PRs + push + weekly cron.

What this adds in CI

After this PR lands, every PR to main will run:

• PHPStan (PHP 8.1) — already gating
• Composer audit + validate — new composer validate --strict step
• PHPUnit (PHP 8.1-8.4 matrix) — already gating
• Coverage (PHP 8.1) — now gating with a 50% line floor (was advisory)
• WPCS on changed PHP files — already gating
• Verify minified assets are up to date — already gating
• Review dependency changes — already gating
• ESLint on assets/js — new, gating
• Vitest on tests/js — new, gating
• Stylelint on assets/css — new, gating
• CodeQL (javascript + php) — new, surfaces findings in the Security tab; not yet required for merge (operator can promote later)

Real bugs caught while implementing

1. ffc-core.js:208 — == instead of === in field-dependency matching (both sides are always strings; no behaviour change, but tightening matters).
2. ffc-dynamic-fragments.js:194 — duplicate var formId shadowing earlier declaration in the same function.
3. ffc-admin.js:91 — redundant var strings redeclare (var hoists, so the second binding was a no-op).
4. ffc-geofence-admin.js:83 — analyzeDateTimeOrder() didn't default time_mode to 'daily' when omitted, drifting from its PHP counterpart in Geofence::analyze_datetime_order(). The metabox form always provides the value, so invisible at runtime — caught by the new unit test.

⚠️ Manual setup required after merge: branch protection on main

This addresses the gap that left Dependabot patch/minor PRs sitting open instead of auto-merging (e.g. #157 last week). dependabot-automerge.yml calls gh pr merge --auto --squash, and --auto only activates when branch protection requires status checks. The MCP tools available to me don't include branch-protection config, so this needs to be set in the GitHub UI:

1. Settings → Branches → Add branch protection rule for main.
2. Enable "Require status checks to pass before merging" and "Require branches to be up to date".
3. Add these as required checks:
   • PHPStan (PHP 8.1)
   • Composer audit
   • PHPUnit (PHP 8.1), PHPUnit (PHP 8.2), PHPUnit (PHP 8.3), PHPUnit (PHP 8.4)
   • Coverage (PHP 8.1)
   • WPCS on changed PHP files
   • Verify minified assets are up to date
   • Review dependency changes
   • ESLint on assets/js
   • Vitest on tests/js
   • Stylelint on assets/css
4. Optional: also require conversation resolution and a pull request before merging.

Once that's in place, the next Dependabot patch/minor will auto-merge as soon as CI is green.

Test plan

• npm run lint:js — 0 errors, 9 unused-vars warnings (non-gating).
• npm run test:js — 23 / 23 OK.
• npm run lint:css — 0 violations.
• vendor/bin/phpunit — 3881 / 9839 OK (no test changes; runs same as on main).
• vendor/bin/phpstan analyse — no errors.
• Coverage floor enforcement — verified inline by reading the workflow; first PR-time run will print the actual percentage on the GitHub Actions step summary.

https://claude.ai/code/session_01HiExaniSqvNBLpVTszCLNx

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