feat(telemetry): add specific PR, issue, and custom tracking IDs for GitHub Actions

[cocosheng-g]

Summary

This PR adds new telemetry attributes to the Gemini CLI to support granular usage metrics for GitHub Actions. These metrics will allow us to track unique Issues and PRs touched by the CLI, and distinguish between different workflow triggers (e.g., Automated vs. Scheduled triage).

Will fix #21130

Details

• Added GEMINI_CLI_GH_EVENT_NAME to EventMetadataKey.
• Added specific tracking IDs: GEMINI_CLI_GH_PR_NUMBER, GEMINI_CLI_GH_ISSUE_NUMBER, and GEMINI_CLI_GH_CUSTOM_TRACKING_ID replacing generic GH_EVENT_NUMBER.
• Updated ClearcutLogger to capture these from environment variables (GITHUB_EVENT_NAME, GH_PR_NUMBER, GH_ISSUE_NUMBER, and GH_CUSTOM_TRACKING_ID).
• The PR/Issue number is logged as a raw string ID (e.g., 123) to avoid fingerprinting PII, relying on the repository context to provide global uniqueness for backend queries.
• Updated telemetry tests in clearcut-logger.test.ts to cover the new environment variables and metadata keys.
• Updated telemetry documentation in docs/cli/telemetry.md.

Related Issues

Related to internal PM request for "Gemini CLI GitHub Action Usage Metric".

How to Validate

1. Run the new tests: npm test -w @google/gemini-cli-core -- src/telemetry/clearcut-logger/clearcut-logger.test.ts
2. Verify that when GITHUB_EVENT_NAME and specific IDs (GH_PR_NUMBER, etc.) are set in the environment, they appear in the Clearcut log metadata as expected.

Example events

Sample 1: api_request (Automated Issue Triage)
Triggered when the CLI sends a prompt to the model during an "Issue Opened" event.

{
  "event_name": "api_request",
  "console_type": "GEMINI_CLI",
  "application": 102,
  "event_metadata": [
    [
      { "gemini_cli_key": 20,  "value": "gemini-1.5-pro" },         // API_REQUEST_MODEL
      { "gemini_cli_key": 39,  "value": "GitHub" },                 // SURFACE
      { "gemini_cli_key": 130, "value": "gemini-triage" },          // GH_WORKFLOW_NAME
      { "gemini_cli_key": 132, "value": "a1b2c3d4..." },            // GH_REPO_HASH
      { "gemini_cli_key": 176, "value": "issues" },                 // GH_EVENT_NAME
      { "gemini_cli_key": 178, "value": "42" }                      // GH_ISSUE_NUMBER (Issue #42)
    ]
  ]
}

Sample 2: api_response (PR Review)
Triggered when the model returns a response for a Pull Request review.

{
  "event_name": "api_response",
  "console_type": "GEMINI_CLI",
  "application": 102,
  "event_metadata": [
    [
      { "gemini_cli_key": 21,  "value": "gemini-1.5-pro" },         // API_RESPONSE_MODEL
      { "gemini_cli_key": 25,  "value": "1240" },                   // INPUT_TOKEN_COUNT
      { "gemini_cli_key": 26,  "value": "450" },                    // OUTPUT_TOKEN_COUNT
      { "gemini_cli_key": 130, "value": "gemini-review" },          // GH_WORKFLOW_NAME
      { "gemini_cli_key": 176, "value": "pull_request" },           // GH_EVENT_NAME
      { "gemini_cli_key": 177, "value": "101" }                     // GH_PR_NUMBER (PR #101)
    ]
  ]
}

Sample 3: start_session (Scheduled Triage)
Triggered when the CLI starts up as part of a cron job (Scheduled).

{
  "event_name": "start_session",
  "console_type": "GEMINI_CLI",
  "application": 102,
  "event_metadata": [
    [
      { "gemini_cli_key": 1,   "value": "gemini-1.5-flash" },       // START_SESSION_MODEL
      { "gemini_cli_key": 130, "value": "gemini-issue-fixer" },     // GH_WORKFLOW_NAME
      { "gemini_cli_key": 176, "value": "schedule" },               // GH_EVENT_NAME
      { "gemini_cli_key": 179, "value": "101,102,103" }             // GH_CUSTOM_TRACKING_ID 
    ]
  ]
}

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (if needed)
• Noted breaking changes (if any)
• Validated on required platforms/methods:
  • MacOS
  • Windows
  • Linux