Make Copilot PR review CLI timeout configurable

[WaelAbuSeada]

Why

Copilot PR review can exceed the current hardcoded 20-minute CLI timeout on larger pull requests (for example, runs with many changed files).

What changed

• Added script env var support: COPILOT_REVIEW_CLI_TIMEOUT_MINUTES (default 30)
• Replaced hardcoded WaitForExit(1200000) with computed timeout based on that variable
• Updated timeout exception message to include the configured value
• Added workflow wiring in CopilotPRReviewRunner.yaml:
  • COPILOT_REVIEW_CLI_TIMEOUT_MINUTES: ${{ vars.COPILOT_REVIEW_CLI_TIMEOUT_MINUTES || '30' }}

Operational guidance

• Default remains bounded at 30 minutes to avoid runaway processes
• For larger PRs, set repository/environment variable COPILOT_REVIEW_CLI_TIMEOUT_MINUTES to 45 or 60 as needed

Validation

• No diagnostics in updated script and workflow files

Fixes AB#635094