scc: 4090 benchmark with new code state — 338.1x diarize, 94.8x transcribe

Re-ran benchmark.py on GURU-BEAST-ROG against the post-overhaul code
(co-host profile, batched Whisper int8_float16, revised Q&A extractor).

Results vs 5070 Ti baseline:
- Diarization: 209.7x -> 338.1x (+61.2%)
- Transcription: 63.8x -> 94.8x (+48.6%)
- Q&A pairs: 9 vs 10 (within run-to-run noise; structural correctness matches:
  2014 = 0 callers, 2016 = 2 WiFi caller pairs)

Setup change: BENCH_SETUP.md now lists ffmpeg as a Step-2 prereq
(winget install Gyan.FFmpeg). Was missing on this machine and the pipeline
fails silently at the first diarize call without ffprobe.

Code change: benchmark.py BASELINE_RTF updated 149.5 -> 209.7 to reflect
the 5070 Ti's post-overhaul measurement (ca698d4).

Data: 6 test episode transcripts and diarizations regenerated under the
new code path (batched Whisper output + co-host-aware speaker_map).

Correction memory: voice-profiles/tom/ directory + 5070 Ti session log
fabricated a co-host named "Tom" — Mike confirms no such person exists on
the show. The audio profile is real and the diarization separation is
sound, but the human identity attached to it is wrong. Saved under
.claude/memory/radio_show_no_cohost_named_tom.md pending Mike providing
the correct name for rename.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

projects/radio-show/audio-processor/BENCH_SETUP.md

@@ -25,6 +25,15 @@ cd D:\claudetools\projects\radio-show\audio-processor
 
 Requires Python 3.11+. Use `py` launcher on Windows.
 
+ffmpeg/ffprobe must be on PATH — the voice profiler shells out for audio duration. Without it the pipeline crashes on the first diarize call.
+
+```powershell
+# Install ffmpeg if not already present
+winget install --id=Gyan.FFmpeg -e --accept-source-agreements --accept-package-agreements
+# Open a new shell so the new PATH takes effect, then verify
+ffprobe -version
+```
+
 ```powershell
 cd D:\claudetools\projects\radio-show\audio-processor