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/index_test_episodes.py

@@ -0,0 +1,102 @@
+"""
+Index the 6 test episodes into archive.db.
+Reads pre-computed transcripts + diarization from test-data/transcripts/.
+"""
+import os, sys, re
+os.environ["PYTHONIOENCODING"] = "utf-8"
+os.environ["TRANSFORMERS_OFFLINE"] = "1"
+if hasattr(sys.stdout, "reconfigure"):
+    sys.stdout.reconfigure(encoding="utf-8")
+
+from pathlib import Path
+from src.indexer import ArchiveIndex
+from src.qa_extractor import load_diarized_transcript, extract_qa_pairs
+from rich.console import Console
+from rich.table import Table
+
+console = Console()
+
+BASE      = Path(__file__).parent
+TRANS_DIR = BASE / "test-data" / "transcripts"
+EP_DIR    = BASE / "test-data" / "episodes"
+DB_PATH   = BASE / "archive.db"
+
+_DATE_RE = re.compile(r"^(\d{4}-\d{2}-\d{2})")
+
+
+def parse_episode_meta(ep_id: str) -> tuple[str, int | None]:
+    """Return (date_str_or_year, hr) from episode directory name."""
+    m = _DATE_RE.match(ep_id)
+    if m:
+        date = m.group(1)
+        hr = int(ep_id[-1]) if ep_id.endswith(("-hr1", "-hr2")) else None
+        return date, hr
+    # season/episode format e.g. 2016-s8e43 — use year only
+    year = ep_id[:4]
+    return year, None
+
+
+console.print(f"\n[bold]Indexing test episodes into {DB_PATH.name}[/bold]")
+
+with ArchiveIndex(DB_PATH) as idx:
+    rows = []
+
+    for ep_dir in sorted(TRANS_DIR.iterdir()):
+        t_path = ep_dir / "transcript.json"
+        d_path = ep_dir / "diarization.json"
+        if not t_path.exists():
+            continue
+
+        ep_id = ep_dir.name
+        date, hr = parse_episode_meta(ep_id)
+        audio_path = EP_DIR / f"{ep_id}.mp3"
+
+        # Episode duration from transcript
+        import json
+        with open(t_path) as f:
+            td = json.load(f)
+        duration = td.get("duration", 0)
+
+        # Register episode
+        idx.add_episode(
+            episode_id=ep_id,
+            audio_path=audio_path,
+            date=date,
+            duration=duration,
+            hr=hr,
+        )
+
+        # Load diarized segments and index
+        segs = load_diarized_transcript(t_path, d_path if d_path.exists() else None)
+        idx.add_segments(ep_id, segs)
+
+        # Extract and index Q&A pairs
+        pairs = extract_qa_pairs(segs)
+        for p in pairs:
+            idx.add_qa_pair(
+                episode_id=ep_id,
+                q_start=p.question_start, q_end=p.question_end,
+                a_start=p.answer_start,  a_end=p.answer_end,
+                question=p.question_text, answer=p.answer_text,
+                topic=p.topic, tags=p.topic_tags,
+            )
+
+        rows.append((ep_id, date, f"{duration:.0f}s", len(segs), len(pairs)))
+        console.print(f"  [green]{ep_id}[/green]: {len(segs)} segs, {len(pairs)} Q&A pairs")
+
+    stats = idx.stats()
+
+table = Table(title="Index Summary")
+table.add_column("Episode")
+table.add_column("Date")
+table.add_column("Duration")
+table.add_column("Segments")
+table.add_column("Q&A")
+for ep_id, date, dur, segs, qa in rows:
+    table.add_row(ep_id, date, dur, str(segs), str(qa))
+
+console.print()
+console.print(table)
+console.print(f"\n[bold]DB totals:[/bold] {stats['episodes']} episodes, "
+              f"{stats['segments']} segments, {stats['qa_pairs']} Q&A pairs")
+console.print(f"[dim]DB path: {DB_PATH}[/dim]")