Build fail-closed multilingual transcription control plane

[Pepstee]

What changed

• adds a provider-neutral, fail-closed long-form transcription control plane
• adds adaptive multilingual English/Russian/Romanian/Korean processing and targeted retry
• adds transcript quality contracts, local adjudication, review packages, diarization boundaries, and evidence-bound benchmarks
• preserves the existing personal-capture review/outbox flow while blocking invalid transcripts from GIGA admission

Why

The previous executor could return structurally valid but semantically defective long-form transcripts, including severe repetition loops. This branch makes semantic quality and provenance explicit and fail-closed.

Validation

• python -m compileall -q dubbing
• python -m ruff check .
• python -m pytest -q — 909 passed, 2 skipped
• python -m build
• Gigabyte offline model-load preflight — ready=true
• Gigabyte 48 kHz mono 32-bit-float ASR+diarization rehearsal — passed

Remaining gates

Real-world multilingual life-logging accuracy and multi-speaker DER/JER remain evidence gates. Cloud upload and GIGA admission stay disabled by default.