fix(token-spy): replace broad exception handlers with specific types

[bugman-007]

Summary

• Replaces all except Exception: with specific exception types
• Complies with CLAUDE.md: "Narrow exceptions at I/O boundaries are fine" but "No broad or silent catches"
• Makes error handling explicit and debuggable

Changes

• JSON parsing (lines 715, 945): except (json.JSONDecodeError, ValueError) instead of except Exception
• File reads (lines 1018, 1116): except (FileNotFoundError, IOError, PermissionError) instead of except Exception
• File writes (line 1143): except (IOError, PermissionError, OSError) instead of except Exception

Rationale

The original code used broad except Exception: handlers at I/O boundaries. While catching exceptions at I/O boundaries is acceptable per CLAUDE.md, they must be specific exception types that map to distinct, meaningful statuses.

Test plan

• Python syntax check passes
• Manual test: token-spy handles malformed JSON responses
• Manual test: token-spy handles missing session files
• Manual test: token-spy handles permission errors on writes

[Lightheartdevs]

Closing as part of v2.1.0 stabilization. We're pausing new feature PRs while we solidify the installer and CI gates. If this is still relevant for v2.2.0 (targeting April 1), please rebase and resubmit. Thank you for contributing.