fix(recorder): retain native frames before readiness

[abrichr]

What changed

A native capture can't report ready until it has stored its first frame and its configured evidence carriers.

This change also keeps each sampled desktop frame and active-window event once. That preserves the source journal's exact ordinals, including the frame before an action and the first frame after it.

Startup now stops with an error after a bounded wait. It cancels pending frame and terminal coordination, and it won't publish a completed producer boundary while a journal producer is still alive.

Why

The hosted Windows run exposed a no-input failure. The recorder announced startup, dropped the first desktop frame, and then rejected its own capture during finalization because no frame remained.

The same retention rule closes ordinal gaps for active-window events and later actions. It doesn't weaken seal verification or accept empty evidence.

Test evidence

• 595 non-browser tests passed; 13 skipped
• Ruff and git diff --check passed
• The focused producer sequence retained three sampled frames as three screen rows and three video writes. Action ordinal 3 binds to frames 2 and 4.
• The exact-head review found no P0-P2 defect.