Android smoke: first fixture capture stalls before any readable snapshot #3831

Android smoke intermittently fails before its first readable capture after opening the fixture. Diagnose and fix the capture/setup boundary without increasing the wait deadline or adding retry-only recovery.

Observed command:

agent-device wait text "Automation lab" 10000 --platform android --serial emulator-5554 --session <session> --daemon-server-mode dual --json

Evidence:

• PR test(ios): speed up fixtures and run native regressions nightly #3824, 14f32fb218ac9e5608012bf6a5805652dc61f7fc: run 39287002936. smoke-android-emulator.test.ts:7:1, scenario smoke:automation-system, COMMAND_FAILED, reason wait_capture_stalled, one capture, zero readable captures, deadline after 10439ms.
• Earlier main, a61556b8fd3268dd0b8032409ad0f0d06107019b: run 39025922562. Same command, scenario, assertion and reason; one capture, zero readable captures, 10232ms poll.
• Both runs retain android-artifacts. Current failure screenshot shows Automation lab; the subsequent diagnostic snapshot succeeds with healthy android-helper capture (619ms helper / 1914ms snapshot). No crash appears in its crash buffer.
• PR test(ios): speed up fixtures and run native regressions nightly #3824 leaves Android runtime, integration scenarios, Android workflow/setup, package manifest and lockfile unchanged from its base a661e43d83735fc74a02118b5698e5d45e03ee21. That exact base's Android run passed. This is evidence of an intermittent pre-existing signature, not proof of infrastructure or a complete root cause.
• Correction: the request NDJSON and daemon log are present under the artifact hidden .agent-device directory. The first scan omitted hidden files. The request shows 2314ms helper install, then 5162ms persistent-session capture including a UiAutomation connection timeout, followed by 2958ms one-shot fallback cancelled at the wait deadline. A different branch's run 39221668804 reports wait_target_absent with a system overlay; do not conflate it with this zero-readable-capture failure.

Required behavior and completion:

• Retain the failed first-capture phase timings and cancellation/setup evidence in CI artifacts.
• Build a cold-open reproduction on an isolated Android emulator and compare unchanged base/head with the same command and no competing tests.
• Identify the owning capture/setup defect and prove the fix with a regression at that boundary and hosted Android smoke.
• Keep deadline/cancellation and failure exits intact. A later successful snapshot alone does not prove infrastructure contention.

Blocks Android validation of #3824. Other lanes and local validation do not replace this obligation.