ci: skip test-local-dev-simulation on non-component PRs

[jeremyeder]

Problem

test-local-dev-simulation runs on every PR (on: pull_request with no paths filter). It does a full make kind-up + integration test suite and takes ~10-15 min. This is unnecessary for docs-only, CI-workflow, or spec changes.

Proposed fix

1. Add a paths filter to .github/workflows/test-local-dev.yml:

   on:
     pull_request:
       paths:
         - 'components/*/Dockerfile'
         - 'components/manifests/**'
         - 'components/backend/**'
         - 'components/operator/**'
         - 'components/frontend/**'
         - 'components/runners/**'
         - 'Makefile'
         - 'tests/**'
         - '.github/workflows/test-local-dev.yml'

2. Update .mergify.yml to handle skipped checks. Mergify's check-success fails when the check doesn't run at all. Options:

   • Use check-success-or-neutral or check-skipped conditions
   • Switch to GitHub branch protection required checks (which handle skipped jobs natively)
   • Add a lightweight "gate" job that always runs and reports success when the path filter skips

Context

Discovered while working on PR #1294 (CI caching improvements) — a workflow-only change was blocked waiting 15+ min for a full kind cluster build that tested nothing relevant.

[github-actions]

🤖 Amber is working on this issue. A PR will be created shortly with the ambient-code:managed label.

[github-actions]

🤖 Amber session completed (phase: Running). View session