Add error handling to AI triage workflow GitHub script

[Copilot]

The workflow script had no error handling for file I/O or API calls, causing failures without informative messages when the agent config file is missing or the GitHub Models API is unavailable.

Changes

• File read: Wrapped fs.readFileSync() in try-catch to handle missing/inaccessible agent config file
• API call: Wrapped github.rest.models.runInference() in try-catch to handle API failures (auth, timeout, rate limits)
• Response validation: Enhanced existing check to include actual response structure in error messages for debugging
• User feedback: All error paths now post issue comments explaining the failure before the workflow fails

Error message example

### ⚠️ AI Triage Error

Failed to connect to the GitHub Models API for AI analysis.

**Error:** Request timeout after 30s

The issue triage could not be completed automatically. A team member will review this issue manually.

Each failure scenario surfaces diagnostic information while maintaining a clear signal that manual review is needed.

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[wadepickett]

Closing. Copilot generated a sperate PR which was not wanted.