radio: rename Tom -> Tara, expand speaker roster

Mike confirmed there is no co-host named "Tom" — the voice in 2014-s6e19
and 2016-s8e43 is Tara. The 5070 Ti session fabricated the Tom identity.
The voice profile itself (44 embeddings, 0.698 cosine vs Mike) is correct;
only the human label was wrong.

Rename swept:
- voice-profiles/tom/ -> voice-profiles/tara/ (git mv preserves all .npy)
- voice-profiles/profiles.json: "Tom" key -> "Tara"
- build_cohost_profile.py: TOM_WINDOWS -> TARA_WINDOWS, COHOST_NAME, comments
- 2026-04-27-qa-extraction-cohost-indexing.md: correction header + body sweep
- 2026-04-27-4090-benchmark-and-test-set.md: closure note
- .claude/memory/radio_show_no_cohost_named_tom.md: resolution + speaker roster

Diarization re-run after rename so speaker_map emits "Cohost: Tara".
Q&A counts unchanged (rename is label-only): 9 pairs across 6 test episodes.

Tara distribution from the post-rename diarization (per-episode % of audio):
  2011-03-12-hr1   140s   5.6%   likely false positive (call-in only)
  2012-03-10-hr1    30s   1.1%   likely false positive (call-in only)
  2012-06-09-hr1   340s  12.8%   suspicious — pending Mike confirm
  2014-s6e19       680s  23.3%   confirmed
  2016-s8e43      1890s  35.5%   confirmed
  2017-s9e30       610s  11.4%   plausible — pending Mike confirm

Broader speaker-roster context Mike provided this session (saved to
memory): the show has had multiple co-hosts (Tara, Randall, Rob) plus
producers/board ops (Andrew, Shannon, Ken, others) who would sometimes
go on-air. Only Tara has a profile so far. Every other speaker is
currently labeled CALLER, which means small CO-HOST attributions in
unexpected episodes (e.g. 2011/2012) may actually be a producer rather
than a false positive — Mike to spot-check.

Action item before full-archive run: build profiles for Randall, Rob,
and the named producers to avoid systematic Q&A false positives in
early-years and 2018/2019 episodes.

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

projects/radio-show/audio-processor/test-data/transcripts/2011-03-12-hr1/diarization.json

@@ -2,8 +2,8 @@
   "num_speakers": 3,
   "speaker_map": {
     "HOST": "HOST",
-    "CALLER": "CALLER",
-    "CO-HOST": "CO-HOST"
+    "CO-HOST": "CO-HOST",
+    "CALLER": "CALLER"
   },
   "turns": [
     {

projects/radio-show/audio-processor/test-data/transcripts/2012-03-10-hr1/diarization.json

@@ -2,8 +2,8 @@
   "num_speakers": 3,
   "speaker_map": {
     "HOST": "HOST",
-    "CALLER": "CALLER",
-    "CO-HOST": "CO-HOST"
+    "CO-HOST": "CO-HOST",
+    "CALLER": "CALLER"
   },
   "turns": [
     {

projects/radio-show/audio-processor/test-data/transcripts/2012-06-09-hr1/diarization.json

@@ -2,8 +2,8 @@
   "num_speakers": 3,
   "speaker_map": {
     "HOST": "HOST",
-    "CALLER": "CALLER",
-    "CO-HOST": "CO-HOST"
+    "CO-HOST": "CO-HOST",
+    "CALLER": "CALLER"
   },
   "turns": [
     {

projects/radio-show/audio-processor/test-data/transcripts/2017-s9e30/diarization.json

@@ -2,8 +2,8 @@
   "num_speakers": 3,
   "speaker_map": {
     "HOST": "HOST",
-    "CALLER": "CALLER",
-    "CO-HOST": "CO-HOST"
+    "CO-HOST": "CO-HOST",
+    "CALLER": "CALLER"
   },
   "turns": [
     {