Add an installable debug APK to every Android PR, plus a PR template

[patrickrb]

Debug APK

This PR changes the workflow file, so it runs the new job itself. Use the "Debug APK" comment CI posts below. It's built from current dev, since this PR doesn't touch app code.

Manual test checklist

1. Wait for the Debug APK for manual testing check to go green. A "Debug APK" comment should then appear on this PR.
2. Open the comment's download link while signed in to GitHub. You should get FT8AF-pr<N>-<sha>-debug.zip.
3. Unzip it and install the .apk on a phone. If the Play Store build is installed, uninstall it first (different signing key). The app should launch, and Settings should show a -dev version.
4. Push another commit to the PR. The same comment should be updated in place, not duplicated, and point to the new SHA.
5. Start a new PR. The description box should be pre-filled with the template sections.

What changed

• .github/workflows/pr-debug-apk.yml (new). On PRs to dev/staging/main that touch ft8af/**, it runs assembleDebug, uploads FT8AF-pr<N>-<sha>-debug.apk as an artifact (kept 30 days), and posts or updates one sticky PR comment with the download link. The existing PR build in android.yml makes an unsigned release APK, which Android refuses to install, so it was no use for testing on a phone. Fork PRs get the APK on the run page but no comment, because their token is read-only.
• .github/pull_request_template.md (new). Sections: Debug APK, a 3-6 step manual test checklist, what changed, risks, and what was tested automatically.
• AGENTS.md. New "Branch names" and "Pull requests" sections: agents never merge, fill in the template, wait for the APK comment, CI must be green, request a Copilot review, and label Discord-sourced PRs from-discord.

android.yml is unchanged. Unit tests (testDebugUnitTest + coverage) and the release build already run on every Android PR there, behind android-gate.

Risks

Low. The change only adds files and has no app code or release-lane changes.

• Don't make Debug APK for manual testing a required check. It's path-filtered at the trigger, so on non-Android PRs it never reports and would block merging. android-gate stays the required check.
• The debug build uses the same applicationId as the Play build but a different signing key. Testers need to uninstall the Play build first, which wipes app data. If that gets in the way, a follow-up could add applicationIdSuffix ".debug" so both can be installed side by side (check Maps and other package-bound keys first).
• Each Android PR adds about one extra build job of Actions minutes.

Tested automatically

• The workflow YAML parses, and .github/scripts/check-agents-md.sh passes locally.
• CI on this PR runs the new job end to end: it builds, uploads, and comments. android.yml doesn't run here because nothing under ft8af/** changed.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 41.51%. Comparing base (0677e40) to head (f6dee78).

Additional details and impacted files

@@            Coverage Diff            @@
##                dev     #924   +/-   ##
=========================================
  Coverage     41.51%   41.51%           
  Complexity      252      252           
=========================================
  Files           280      280           
  Lines         33993    33993           
  Branches       4034     4034           
=========================================
  Hits          14112    14112           
  Misses        19592    19592           
  Partials        289      289           

Flag	Coverage Δ
native	9.93% <ø> (ø)

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[github-actions]

Debug APK

Download FT8AF-pr924-f6dee78-debug.zip (built from f6dee78, run)

Unzip it and install the .apk on the phone. The download needs a signed-in GitHub account, and the link expires after 30 days.
This build is signed with a debug key. If the Play Store build is installed, uninstall it first; Android will not install over an app signed with a different key.