ci: run demo + showcase on shiplight-small and wire failure triage

[feng-shiplight]

Runs the showcase suite in CI alongside demo, moves to a smaller runner, and
wires up automated failure triage.

Test workflow (yaml-examples.yml)

• shiplight-medium → shiplight-small
• Runs --project demo --project showcase --workers=2. setup still runs
  automatically as a dependency of demo. 24 + 18 = 42 tests.
• timeout-minutes 30 → 60. The old value was sized for demo alone, and
  playwright.config.ts allows each test 10 minutes.
• npm install → npm ci, matching what the triage autofix job runs, so
  lockfile drift breaks this workflow first instead of only the repair path.
• Replaces the full e2e-report artifact with ci-triage/upload-report, which
  drops traces (*.zip) and videos (*.webm). Keeping both would defeat the
  purpose: triage runs gh run download with no name filter, so it would pull
  the heavy copy anyway. Full traces and videos still reach the Shiplight cloud
  report via the retained npx shiplight report step, but they are no longer
  downloadable from the GitHub run.

Triage workflow (ci-failure-triage.yml, new)

Watches YAML Examples Tests and calls ShiplightAI/ci-triage@v1.2. On a red
run an agent diagnoses each failure from the logs and the uploaded report, and
for failures it classifies as fixable spec issues it applies the fix, re-runs
the test, and opens a PR. It never auto-merges.

The Shiplight project is not at the repository root, so this passes
working-directory: yaml-examples. allowed-paths is relative to that and is
scoped to demo showcase templates — what the fix agent is actually permitted
to edit, not helpers/ or the fixture directories. No extra_env: the demo
suite logs into saucedemo with public credentials and showcase hits public
sites, so the autofix re-run needs no app secrets.

Other

• showcase/17-non-standard-clickable had base_url: http://localhost:3000, a
  leftover from local development that nothing serves in CI. The same page is
  published at https://static.shiplight.ai/testing/interactions/non-standard-clickable.html,
  which every other showcase test already uses.
• Removes the two Playwright example workflows.
• Bumps shiplightai to ^0.1.99 and regenerates the lockfile.
• Gitignores .mcp.json alongside the other agent tooling.

Not yet verified

The shiplight-small runner, whether all 42 tests pass at 2 workers, and
whether 60 minutes is enough — this PR's own run is the first test of all three.

Triage will not run on this PR. workflow_run only reads workflow files from
the default branch, so ci-failure-triage.yml stays dormant until this merges.

🤖 Generated with Claude Code