test: verify RN Android watch-root walk-up in find-projects

[ksroda-sa]

Purpose

Test PR — not for merge. Verifies the most subtle case in the path-aware find-projects logic:

A change inside a React Native sample but outside its android/ subdirectory should still trigger the Android assembleDebug build via the watch_root walk-up (91b01af on PR #161).

What this changes

Adds a one-line cross-link in samples/react-native/login-pkce/README.md. The change lives at the RN sample root, not in samples/react-native/login-pkce/android/.

Expected behavior

Workflow	find-projects expected matrix	test/build expected	Aggregator
test-android	["samples/react-native/login-pkce/android"] (walk_root finds package.json one level up → matches README)	runs assembleDebug for that one project	Android tests passed ✅
test-js	["samples/react-native/login-pkce"] (direct match — README is in the project subtree)	runs yarn install + build for that one project	JS tests passed ✅
test-ios	[] (no iOS sample touched)	skipped	iOS tests passed ✅ via result == 'skipped'
test-dotnet	[]	skipped	.NET tests passed ✅ via skip
test-java	[]	skipped	Java tests passed ✅ via skip
extract	n/a	runs validate	validate ✅

What this PR exercises

• ✅ Watch-root walk-up: RN Android gradlew lives at samples/react-native/login-pkce/android/gradlew, but the walk-up finds samples/react-native/login-pkce/package.json and uses that as the watch_root. README change there must include the Android project in the matrix.
• ✅ Per-project narrowing: samples/react-native/token-refresh should NOT appear in either matrix (only login-pkce's subtree was touched).
• ✅ Cross-framework filter: native Android samples (samples/android/*) should NOT appear in test-android's matrix (their watch_root is the project dir itself, README is not in their subtree).
• ✅ Skip-as-success aggregator: iOS/.NET/Java workflows produce empty matrices → test job skipped → aggregator's result != 'success' && result != 'skipped' branch is false → aggregator job exits cleanly → required check is green.

Test result observation

If aggregators all green and test-android matrix contains exactly one entry (samples/react-native/login-pkce/android), the watch-root logic is verified end-to-end and we can close this PR.

If the matrix is empty or contains other unrelated projects, there's a regression to investigate.

🤖 Generated with Claude Code