fix(gsd): Make task completion robust to malformed evidence JSON

[aryanjsingh]

Summary

Fixes a crash in the gsd_task_complete tool when smaller models generate malformed numeric values in verificationEvidence. The schema for exitCode and durationMs is updated to accept strings, and the handler now coerces these values to numbers, preventing parsing errors and improving reliability.

Changes

• src/resources/extensions/gsd/db-tools.ts: Updated the VerificationEvidenceSchema to allow exitCode and durationMs to be either a number or a string. This prevents schema validation failures when the language model provides a numeric value as a string (e.g., "0" instead of 0) or syntactically invalid JSON like a bare minus sign.
• src/resources/extensions/gsd/tools/complete-task.ts: Added coercion logic at the beginning of handleCompleteTask to normalize exitCode and durationMs to numbers. This handles cases where the model provides a string or a malformed value (like a bare -), ensuring data consistency before it's used or stored in the database.

Related Issue

Closes #3464

[github-actions]

🟢 PR Risk Report — LOW

Files changed	2
Systems affected	0
Overall risk	🟢 LOW