fix(runner): fix credential retry error message and observability end_turn import

- auth.py: don't retry with fresh CP token when caller-token BOT_TOKEN
  fallback fails; preserve that path's original error message
- observability.py: guard claude_agent_sdk import in end_turn with try/except
  so Langfuse generation.update() is still called when the SDK is not installed

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: Ambient Code Bot

components/runners/ambient-runner/ambient_runner/observability.py

@@ -515,14 +515,19 @@ def end_turn(
             return
 
         try:
-            from claude_agent_sdk import TextBlock
+            # Extract text content — TextBlock is optional (claude_agent_sdk may not be installed)
+            try:
+                from claude_agent_sdk import TextBlock as _TextBlock
+            except ImportError:
+                _TextBlock = None
 
-            # Extract text content
             text_content = []
             message_content = getattr(message, "content", []) or []
             for blk in message_content:
-                if isinstance(blk, TextBlock):
+                if _TextBlock is not None and isinstance(blk, _TextBlock):
                     text_content.append(getattr(blk, "text", ""))
+                elif hasattr(blk, "text") and isinstance(getattr(blk, "text", None), str):
+                    text_content.append(blk.text)
 
             output_text = (
                 "\n".join(text_content) if text_content else "(no text output)"

components/runners/ambient-runner/ambient_runner/platform/auth.py

@@ -174,16 +174,6 @@ def _do_req():
                 try:
                     with _urllib_request.urlopen(fallback_req, timeout=10) as resp:
                         return resp.read().decode("utf-8", errors="replace")
-                except _urllib_request.HTTPError as fallback_err:
-                    if fallback_err.code in (401, 403):
-                        return _retry_with_fresh_bot_token(fallback_err.code)
-                    logger.warning(
-                        f"{credential_type} BOT_TOKEN fallback also failed: {fallback_err}"
-                    )
-                    raise PermissionError(
-                        f"{credential_type} authentication failed: caller token expired "
-                        f"and BOT_TOKEN fallback also failed"
-                    ) from fallback_err
                 except Exception as fallback_err:
                     logger.warning(
                         f"{credential_type} BOT_TOKEN fallback also failed: {fallback_err}"