refactor(src): narrow exception types in Phase 7 batch (8 sites across 7 files)

Migrates the 8 try/except sites in Infrastructure + Hook + Utility
files by narrowing the exception types from broad 'except Exception'
to specific stdlib/domain exceptions.

Files and sites:
1. src/api_hooks.py:453 (HookHandler.do_GET error response)
   except Exception -> except (OSError, ValueError)
2. src/api_hooks.py:826 (HookHandler.do_POST error response)
   except Exception -> except (OSError, ValueError)
3. src/api_hooks.py:916 (websocket connection cleanup)
   except Exception -> except (OSError, ValueError)
4. src/file_cache.py:84 (path mtime stat)
   except Exception -> except (OSError, ValueError)
5. src/orchestrator_pm.py:37 (track metadata.json read)
   except Exception -> except (OSError, json.JSONDecodeError, UnicodeDecodeError)
6. src/orchestrator_pm.py:49 (track spec.md read)
   except Exception -> except (OSError, UnicodeDecodeError)
7. src/outline_tool.py:67 (ast.unparse node.returns)
   except Exception -> except (ValueError, TypeError)
8. src/outline_tool.py:90 (ast.unparse ImGui context)
   except Exception -> except (ValueError, TypeError, AttributeError)
9. src/shell_runner.py:99 (subprocess cleanup on error)
   except Exception -> except (OSError, subprocess.SubprocessError)
10. src/summarize.py:187 (summarise_file fallback)
    except Exception -> except (OSError, ValueError, TypeError, AttributeError)
11. src/summarize.py:191 (summarise_file outer)
    except Exception -> except (OSError, ValueError, TypeError)

Decisions:
- src/api_hook_client.py: 0 violations; 2 compliant sites; no migration
- src/hot_reloader.py:58 - kept except Exception (module reload can
  raise any exception; test fixture uses generic Exception)
- src/api_hooks.py:938-941 - RETHROW (keep as-is; cascading if changed)

Tests verified:
- tests/test_outline_tool.py (3 tests) PASS
- tests/test_hot_reloader.py (8 tests) PASS
- tests/test_hot_reload_integration.py (13 tests) PASS

src/file_cache.py

@@ -81,7 +81,7 @@ class ASTParser:
   try:
    p     = Path(path)
    mtime = p.stat().st_mtime if p.exists() else 0.0
-  except Exception:
+  except (OSError, ValueError):
    mtime = 0.0
 
   if path in _ast_cache: