ci: staged-release pipeline with deployed-URL E2E gate, prod smoke, and rollback (ADR-0001)

[MrCoder]

Imitates conf-app's transferable release practices on the Firebase stack (not its Cloudflare/Forge mechanics). Motivated by the recent risky prod deploy that spawned rollback-prod. Full rationale + rejected alternatives in docs/adr/0001-release-pipeline-imitating-conf-app.md.

New flow

merge master → deploy staging → E2E gate (staging.zenuml.com, full suite)
            → gate green → auto-create draft release-<ts> + extension.zip
            → human clicks Publish → deploy-prod → @smoke check (app.zenuml.com)

Changes

• playwright.config.js — PW_BASE_URL env + conditional webServer; one spec serves local / staging-gate / prod-smoke.
• e2e/tests/smoke.spec.js — tag a fast read-only @smoke subset (load + render + core-bundle).
• deploy-staging.yml — restrict to master+PRs, never-cancel-master concurrency, staging E2E gate, auto-draft release.
• deploy-prod.yml — post-deploy @smoke job against production.
• rollback-prod.yml (new) — workflow_dispatch re-deploys a chosen prior release-* across all surfaces (hosting + functions + Firestore rules), with post-rollback smoke.
• ADR-0001 (new) + README/CLAUDE.md deployment sections + release-app skill rewritten to draft-publish.

Key decision: deployed-URL gate is chromium-only

Verified against live staging: the full 3-browser suite has webkit hard-fail + firefox flakiness on network-timed localStorage/render tests (a remote-target artifact — the 3-browser suite is green locally on PRs). Scoping the deployed gate to chromium keeps "did the deploy work?" reliable without blocking every release on cross-browser flake. Cross-browser correctness stays covered by the local PR run.

Verification (local)

• ✅ All 3 workflows parse; jobs/triggers as expected.
• ✅ @smoke selects 9 (3×3), full suite 96; env toggle confirmed (local→localhost+webServer, remote→URL+no webServer).
• ✅ @smoke green against live prod (chromium, 3 passed, 5.6s).
• ✅ Full suite green against live staging (chromium, 31 passed, 1 flaky retried).

Not verifiable without a real Actions run: deploy steps, gh release create, artifact pass-through, concurrency behavior — these first exercise on merge to master. actionlint not installed locally.

🤖 Generated with Claude Code