Fix workflow failure when GCP_CREDENTIALS secret is unset

[Copilot]

The "Dump GH CI Stats" workflow fails with SyntaxError: Unexpected end of JSON input when the GCP_CREDENTIALS secret is not configured, as JSON.parse('') throws on empty strings.

Changes

• dump-ci-stats-to-gcp-metrics.cjs: Validate credentials before parsing, exit gracefully if unset
• gcp-monitoring.cjs: Same validation, exports stub functions to prevent import failures

Both scripts now:

1. Check for empty/whitespace-only values before parsing
2. Wrap JSON.parse() in try-catch for malformed JSON
3. Load @google-cloud/monitoring only after validation succeeds

// Before
const gcpCredentials = JSON.parse(process.env.GCP_CREDENTIALS);

// After
if (!process.env.GCP_CREDENTIALS || process.env.GCP_CREDENTIALS.trim() === '') {
  console.log('GCP_CREDENTIALS not set. Skipping metrics reporting.');
  process.exit(0);
}

let gcpCredentials;
try {
  gcpCredentials = JSON.parse(process.env.GCP_CREDENTIALS);
} catch (error) {
  console.error('Failed to parse GCP_CREDENTIALS:', error.message);
  process.exit(0);
}

Since these are optional monitoring features, workflows now skip metrics reporting when credentials are unavailable rather than failing.

Original prompt

Reference: https://github.com/Snapp949/agoric-sdk/actions/runs/22012754432/job/63609548053#step:6:1

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