fix(render): expose capture calibration progress

[miguel-heygen]

RCA

Auto-worker renders reported Starting frame capture at 25% before capture-cost calibration. Calibration can spend over a minute initializing Chrome and writes throwaway sample frames, while the final-output counter correctly remains zero. That combination made a healthy render look stalled.

Fix

• report Calibrating capture performance before the eligible auto-worker calibration branch
• keep final-output framesRendered at zero during throwaway sampling
• preserve every existing calibration skip gate and normal capture progress

Regression coverage

• eligible auto-worker calibration emits the dedicated stage and resets only final-frame accounting
• explicit-worker renders skip calibration without mutating progress

Verification

• producer unit suite: 297 Vitest assertions plus all Bun unit lanes passed
• producer typecheck passed
• oxlint and oxfmt passed
• fallow strict all-findings audit passed
• independent code review: no findings after test-seam revision