Folds the #370 root-cause finding into the spike. The stable `e2e` matrix
retries its test run once; `e2e-preview` runs connectedDebugAndroidTest exactly
once, so a flaky test self-heals on API 29-36 but wedges the required gate on
API 37 (e.g. #370's SignaturesScreenTest teardown race).
Doc: adds risk item 9 (retry-parity gap + its sharding interaction — per-test
flake is NOT amplified by sharding unlike boot flake, and a per-shard retry
costs only B + T/N; framed mitigation-not-fix) and two §6 recommendations
(retry parity, mirrored into api37_e2e.py; adb start-server before the boot
loop).
PoC (ci.yml): per-shard single test retry (::warning:: on retried-but-passed)
+ adb start-server before the boot loop. The api37_e2e.py retry mirror stays a
documented recommendation (local path needs a real-emulator validation this
spike did not boot). Still DRAFT, not auto-merged.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
JMR-devandClaude Opus 4.8
0e9f54e686