fix(voice): stop backtick TTS crash and actually count error turns

Claude replies with markdown/backticks by default; MeloTTS's Korean text
normaliser has no entry for '`' and dies with KeyError: '`', so any reply
mentioning a command/code block crashed the whole voice turn (500 on
/api/voice-turn). Fix at the shared synth() choke point with
normalize_for_speech(), which flattens code fences/inline code/links/markdown
and guarantees no backtick reaches the worker — covering both the dashboard
voice turn and the Discord speak() bridge. Also add a PERSONA line asking the
model to avoid markdown (belt-and-suspenders; the code strip is the real fix).

errors_total never moved for turn-level failures: it was only bumped by
log("error") events, and the dashboard voice path calls turn.finish(error=...)
without logging. Emit one error-level log event from Turn.finish() when a turn
ends in error, so both the server counter and the browser SSE mirror stay
consistent, guarded to count at most once. Drop the now-redundant pipeline
log("error") to avoid double counting and remove the dead _publish stub.

Verified: raw backtick -> worker KeyError '`' reproduced; after fix real
MeloTTS synth of a backtick+fenced reply succeeds; /api/voice-turn returns 200
with a wav body on a backtick reply and errors_total stays 0, and an induced
synth failure returns 500 with errors_total incrementing to exactly 1. Full
suite 18 passed.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/test_monitor.py

@@ -72,6 +72,30 @@ def test_monitor_marks_errors():
     assert snap["status"]["errors_total"] >= 1
 
 
+def test_error_turn_increments_errors_total_once():
+    """The dashboard voice turn (dashboard.voice_turn) records a turn and calls
+    turn.finish(error=...) directly — it never goes through the pipeline's
+    log("error") path. That failure must still land in errors_total, and exactly
+    once no matter how many times the turn is re-published."""
+    mon = Monitor()
+    turn = mon.turn(source="discord")
+    turn.heard("`코드` 얘기")           # touches/publishes again
+    turn.replied("답변")                 # and again
+    assert mon.status_snapshot()["errors_total"] == 0
+
+    turn.finish(error="melo synth failed: KeyError '`'")
+    assert mon.status_snapshot()["errors_total"] == 1
+
+    # A stray re-finish/re-publish must not double count.
+    turn.finish(error="melo synth failed: KeyError '`'")
+    turn._touch()
+    assert mon.status_snapshot()["errors_total"] == 1
+
+    # The failure is also visible as an error-level event for the live feed.
+    events = mon.snapshot()["events"]
+    assert any(e["type"] == "log" and e["level"] == "error" for e in events)
+
+
 def test_subscriber_receives_live_turn_events():
     async def go():
         mon = Monitor()