perf(ios): remove extra recording uptime request by returning a runner timing anchor

[thymikee]

What to build

Avoid the extra iOS runner uptime request currently used only to anchor touch-overlay recording timing.

This is separate from readiness preflight. The optimization should move the timing anchor into an existing recording or gesture lifecycle path, such as returning a runner uptime anchor from recordStart or deriving the anchor from the first runner gesture response when touch-overlay recording is enabled.

Performance target: starting an iOS simulator recording with touch overlays should avoid a standalone uptime runner command while preserving accurate gesture overlay timing.

Acceptance criteria

• Touch-overlay recording no longer requires a separate standalone uptime command only for clock anchoring when a runner-provided timing anchor is available.
• Gesture overlay timing remains correct for simulator recordings with one or more gestures.
• Existing fallback behavior remains available when the runner timing anchor is missing or unusable.
• Recording start/stop behavior and output shape remain compatible with existing callers.
• Focused tests cover the new timing-anchor path and the fallback path.
• iOS simulator validation starts a recording with touch overlays, performs at least one gesture, stops the recording, and confirms the overlay timing is usable while one fewer runner request is emitted during setup.

Blocked by

None - can start immediately