fix(test-manifest): register missing capabilities to unblock CI

[yangkaa]

What

The Check test manifest CI step (make test-manifest-check) was failing on main because three managed tests carry capability_id markers that were never registered in test-manifest.json:

• rainbond.dockerfile-build.registry-mirror-toml — builder/sources/buildkit_toml_test.go
• rainbond.upgrade-configmap-aggregates-create-update-errors — worker/appm/controller/upgrade_test.go
• rainbond.upgrade-service-aggregates-create-update-errors — worker/appm/controller/upgrade_test.go

Reference failing run: https://github.com/goodrain/rainbond/actions/runs/27359033207/job/80841118118

Changes

• test-manifest.json: register the three capabilities (interface / code_paths / tests), inserted in sorted order.
• test-manifest.md: regenerated via scripts/manage_test_manifest.py render to stay in sync.
• CLAUDE.md / AGENTS.md: document the CI-enforced test-manifest workflow so future managed tests are registered with scripts/manage_test_manifest.py add instead of hand-editing the manifest (which is what caused this failure).

Test plan

• make test-manifest-check → test manifest validation passed for rainbond
• python3 -c "import json; json.load(open('test-manifest.json'))" → valid JSON
• No reformatting churn: diff is additive only (+163 lines across 4 files)