fix(automation): stabilize video page readiness

[dorakoo]

Summary

• add a nine-stage bounded video-page readiness state machine
• persist redacted per-stage diagnostics and distinct failure codes
• allow one bounded pre-submit recovery while preserving fail-closed no-resend semantics

Validation

• targeted: 3 files / 189 tests pass
• validate: 48 files / 1012 tests pass
• ESLint: 0 errors / 147 warnings
• renderer/main build and Windows pack pass
• joint P2/P3 real acceptance: one 5s submission, same-conversation restart recovery, no duplicate send

Dola remains unverified. No credentials, sessions, task ledgers, artifacts, or acceptance copies are included.