radio show: co-host voice profile, Q&A extraction fixes, archive index

- Build Tom (co-host) voice profile (44 embeddings, 0.698 similarity to Mike)
- diarizer.py: add CO-HOST speaker label for cohost-role profiles
- voice_profiler.py: emit "Cohost: <name>" label for cohost role
- qa_extractor.py: overlap resolution at load time (midpoint boundary split),
  4s CALLER-preference threshold, turn-based caller-intro lookback (2 HOST turns),
  _preceded_by_caller_intro() helper, _PHONE_GREETING pattern,
  751-1041 + "we'll get your problem solved" promo signatures
- benchmark.py: use src.transcriber.transcribe with batch_size=16
- add index_test_episodes.py and build_cohost_profile.py scripts
- add .gitignore (exclude episodes, transcripts, *.db, .venv)
- session log: 2026-04-27-qa-extraction-cohost-indexing.md

Result: 2016-s8e43 drops from 12 false-positive Q&A pairs to 2 real caller pairs.
archive.db: 6 episodes, 762 segments, 10 Q&A pairs, FTS5 search verified.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

projects/radio-show/audio-processor/voice-profiles/profiles.json

@@ -1,26 +1,34 @@
-{
-  "Mike Swanson": {
-    "role": "host",
-    "num_samples": 180,
-    "source_episodes": [
-      "2010-10-02-hr1.mp3",
-      "2011-06-04-hr1.mp3",
-      "2011-09-10-hr1.mp3",
-      "2014-s6e05.mp3",
-      "2015-s7e30.mp3",
-      "2016-s8e42.mp3",
-      "2017-s9e26.mp3",
-      "2018-s10e17.mp3",
-      "2018-s10e21.mp3",
-      "2010-10-02-hr1.mp3",
-      "2011-06-04-hr1.mp3",
-      "2011-09-10-hr1.mp3",
-      "2014-s6e05.mp3",
-      "2015-s7e30.mp3",
-      "2016-s8e42.mp3",
-      "2017-s9e26.mp3",
-      "2018-s10e17.mp3",
-      "2018-s10e21.mp3"
-    ]
-  }
+{
+  "Mike Swanson": {
+    "role": "host",
+    "num_samples": 180,
+    "source_episodes": [
+      "2010-10-02-hr1.mp3",
+      "2011-06-04-hr1.mp3",
+      "2011-09-10-hr1.mp3",
+      "2014-s6e05.mp3",
+      "2015-s7e30.mp3",
+      "2016-s8e42.mp3",
+      "2017-s9e26.mp3",
+      "2018-s10e17.mp3",
+      "2018-s10e21.mp3",
+      "2010-10-02-hr1.mp3",
+      "2011-06-04-hr1.mp3",
+      "2011-09-10-hr1.mp3",
+      "2014-s6e05.mp3",
+      "2015-s7e30.mp3",
+      "2016-s8e42.mp3",
+      "2017-s9e26.mp3",
+      "2018-s10e17.mp3",
+      "2018-s10e21.mp3"
+    ]
+  },
+  "Tom": {
+    "role": "cohost",
+    "num_samples": 44,
+    "source_episodes": [
+      "2014-s6e19.mp3",
+      "2016-s8e43.mp3"
+    ]
+  }
 }