[Release] Add Play pre-launch report runbook

[jjoonleo]

Advances #459.
Refs #467.

Summary

• Add a Play Console pre-launch report runbook for the [Release] Run Play Console pre-launch report and resolve blockers #459 release gate.
• Add an evidence template covering report URL, build identity, crashes, ANRs, policy warnings, severe accessibility warnings, accepted risks, and follow-up issues.
• Link the runbook from the docs index and release checklist.
• Record the issue-specific plan under plans/.

Verification

• git diff --check

Remaining human tasks

• Complete [Release] Lock initial production versioning #453 and [Release] Build a signed release Android App Bundle #452 so the signed release AAB exists and is uploaded to Google Play Internal Testing or Closed Testing.
• Use Play Console access to run or wait for the pre-launch report for the uploaded build.
• Record evidence using docs/Play-Pre-Launch-Report.md.
• Fix release-blocking findings in follow-up issues or explicitly accept non-blocking findings as the release owner.

Status

This PR advances #459 with the repo artifact Codex can produce, but #459 remains externally blocked until Play Console access and the uploaded AAB are available.