0.4.0 - Decode collapse fix, pinned dependencies, diarization removed

Fixes the transcription collapse that produced 0.15 to 1.24 words/sec on some recordings. Validated on the GPU host against the 755 s reference file at 2.75 words/sec with per-pass confidence 0.97 to 0.98.

Decode

• Removed the audio preprocessing stage. Its noise gate measured the speech itself, so every file went through an unprofiled denoise and a second lossy encode.
• Temperature is now passed as a fallback ladder, so faster-whisper can recover from a collapsed decode instead of being locked to one attempt.
• Removed the single-speaker initial prompt.
• Pass 5's condition_on_previous_text setting is now honored.

Quality gate

• Added a words-per-second floor (MIN_WORDS_PER_SEC, default 1.0) alongside the alphanumeric check, routed through the same retry and quarantine path.

Build

• Direct dependencies pinned to the package set captured from the working container (torch 2.12.1, ctranslate2 4.8.0, faster-whisper 1.2.1).
• Speaker diarization removed. It had been failing silently in production and the multi-speaker path never ran. The build no longer needs a Hugging Face token.
• LD_LIBRARY_PATH puts the conda lib directory first; the v3.4.1 base's numpy needs a newer libstdc++ than Ubuntu 20.04 provides.
• Flask debug mode off by default.
• Dockerfile.release added as the documented source-only hotfix path.

Docs

• docs/SESSION_KNOWLEDGE.md with the diagnosis, the validation recipe, and the validation record.