Adopt reusable CI standard (#30)

Squash-merged from claude/adopt-ci-20260616.

QA-approved; all CI checks green on 3b4e3f04.

Agent-Session: deploy-ci-rollout-news-plugin-2026-06-16

CHANGELOG.md

@@ -0,0 +1,30 @@
+# Changelog
+
+All notable changes to Peptide News Plugin are documented here.
+Format: [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
+Versioning: [Semantic Versioning](https://semver.org/).
+
+## [2.5.0] — 2026-06-16
+
+### Changed
+- **CI standardization (estate wave 2):** Replace per-repo CI jobs in
+  `ci.yml` with a thin caller of `peptiderepo/peptide-e2e/.github/workflows/ci.yml@main`
+  (`tests: stubs`, `has_js: true`). Adds `workflow_call` trigger so `deploy.yml`
+  gate remains valid.
+- Extract `security-audit` job from `ci.yml` into standalone
+  `.github/workflows/security-audit.yml` (kept as-is, unique to this repo).
+- `deploy.yml`: elevate permissions to `contents: write` so the nested
+  phpcbf commit-back step in the reusable workflow receives the correct token scope.
+- `composer.json`: pin `test` script to `vendor/bin/phpunit --configuration phpunit.xml.dist`
+  for explicit path resolution in CI; pin `lint` / `lint:fix` to `vendor/bin/`.
+- `phpunit.xml.dist`: add XSD reference for PHPUnit 9.6; drop deprecated
+  `convertErrorsToExceptions`, `convertNoticesToExceptions`, `convertWarningsToExceptions`
+  attributes.
+
+### Notes
+- `rollback.yml` and `cto-review.yml` and `main-push-audit.yml` unchanged — unique / estate-separate.
+- No functional code changes in this commit.
+
+## Prior history
+
+Versions prior to 2.5.0 were not tracked in a CHANGELOG. See git log for details.