fix(api_server): replace bare except: with specific exception types

[Teerapat-Vatpitak]

Summary

• Replaces three bare except: clauses in agent/api_server.py with explicit exception classes.
• Pure code-quality change; no behaviour change for the failures these blocks are meant to swallow; KeyboardInterrupt / SystemExit / programming bugs now propagate as they should.

Why

Three blocks in api_server.py use bare except: — which catches BaseException subclasses including KeyboardInterrupt, SystemExit, and GeneratorExit. That makes the API server unresponsive to Ctrl+C inside these blocks and silently hides real bugs (NameError, AttributeError) as no-op passes.

The blocks themselves are best-effort metadata extraction from per-run artifact files where falling through with the default value is the right behaviour — but only for the specific I/O / parse failures these blocks can actually produce. Tightening the catch surface preserves that intent while removing the foot-gun.

Changes

Line	Block	Before	After
1015	req.json prompt extraction	except:	except (json.JSONDecodeError, OSError):
1022	planner_output.json prompt extraction	except:	except (json.JSONDecodeError, OSError):
1042	metrics.csv numeric parse	except:	except (OSError, ValueError):

The other except Exception: clauses in this file (e.g. lines 638, 730, 745) already exclude BaseException and are out of scope for this PR.

Test plan

• pytest --ignore=agent/tests/e2e_backtest --tb=line -q passes — test_settings_api, test_security_auth_api, and test_upload_api all still green.
• grep -nE '^\s+except:\s*$' agent/api_server.py returns no matches.

Checklist

• No changes to protected areas.
• No new dependencies / hardcoded values.
• Code follows CONTRIBUTING.md (Conventional Commit prefix fix:, no comment-preserved code).
• Documentation updated — N/A.

[warren618]

Thanks for the cleanup. The narrowed exception handling keeps the intended best-effort behavior while avoiding bare except: swallowing BaseException. I verified the affected API tests and syntax checks before merging.