fix(whatsapp-cloud): review follow-ups for #43921

- nous_subscription: gate the STT managed-default flip on openai-audio
  entitlement and skip when a local backend (faster-whisper or custom
  command) works; new _local_stt_backend_available() helper + tests
- whatsapp_cloud: WHATSAPP_CLOUD_{DM_POLICY,ALLOW_FROM,GROUP_POLICY,
  GROUP_ALLOW_FROM} env overrides so both adapters can run in parallel;
  normalize allowlist entries (JID/punctuation) to bare wa_id
- whatsapp_cloud: wrap per-message event build in try/except (dedup-marked
  wamids would be silently dropped on Meta's batch retry otherwise)
- whatsapp_cloud: validate media_id before URL/filename interpolation,
  delete transient .ogg after voice upload, FIFO-cap interactive-button
  state dicts and per-chat wamid cache
- whatsapp_common: '# **Title**' headers no longer double-wrap asterisks
- setup wizard: read access token / app secret via getpass on TTYs
- docs: new WHATSAPP_CLOUD_* gating env vars

gateway/platforms/whatsapp_common.py

@@ -342,8 +342,18 @@ class WhatsAppBehaviorMixin:
         # _text_ is already WhatsApp italic — leave as-is
 
         # --- 4. Convert markdown headers to bold text ---
-        # # Header → *Header*
-        result = re.sub(r"^#{1,6}\s+(.+)$", r"*\1*", result, flags=re.MULTILINE)
+        # # Header → *Header*. Strip any *...* wrapping already produced
+        # by step 3 (e.g. "# **Title**" → "*Title*", not "**Title**",
+        # which WhatsApp renders with literal asterisks).
+        def _header_to_bold(m: re.Match) -> str:
+            inner = m.group(1).strip()
+            while len(inner) > 1 and inner.startswith("*") and inner.endswith("*"):
+                inner = inner[1:-1].strip()
+            return f"*{inner}*"
+
+        result = re.sub(
+            r"^#{1,6}\s+(.+)$", _header_to_bold, result, flags=re.MULTILINE
+        )
 
         # --- 5. Convert markdown links: [text](url) → text (url) ---
         result = re.sub(r"\[([^\]]+)\]\(([^)]+)\)", r"\1 (\2)", result)