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>

wsai/monitor.py

@@ -88,6 +88,7 @@ class Turn:
         self.error = ""
         self.total_ms = 0.0
         self._steps: list[Step] = []
+        self._error_logged = False  # count this turn's failure at most once
 
     # -- recording API (called from the pipeline) ------------------------- #
     def heard(self, text: str) -> None:
@@ -108,8 +109,19 @@ class Turn:
             self.error = error
         elif any(s.ok is False for s in self._steps):
             self.status = "error"
+            if not self.error:
+                failed = next((s for s in self._steps if s.ok is False), None)
+                self.error = (failed.error if failed else "") or "step failed"
         else:
             self.status = "ok"
+        # A turn that ended in error must be reflected in errors_total. That
+        # counter is driven by error-level log events on BOTH the server
+        # (Monitor.log) and the browser (dashboard SSE handler), so emit one
+        # log event here rather than bumping a counter the client won't mirror.
+        # Guarded so the repeated _touch()/finish() calls can't double-count.
+        if self.status == "error" and not self._error_logged:
+            self._error_logged = True
+            self._monitor.log("error", f"대화 #{self.id} 실패: {self.error}")
         self._touch()
 
     # -- internal --------------------------------------------------------- #
@@ -185,11 +197,8 @@ class Monitor:
         return t
 
     def _publish(self, t: Turn) -> None:
-        # Recompute error total lazily on error transitions.
-        if t.status == "error":
-            with self._lock:
-                # errors_total counts turns that ended in error at most once
-                pass
+        # errors_total is bumped once when the turn transitions to error, inside
+        # Turn.finish() (via a log event), so this only streams the turn state.
         self._broadcast({"type": "turn", "turn": t.to_dict()})
 
     # -- snapshot / subscribe (read side, HTTP threads) ------------------- #