Resolve OTLP export failures instead of rejecting

[alexanderMontague]

WHY are these changes introduced?

Related to incident #inv-18682 (February 2026 OTLP failures). Stacks on #6851.

When the OTLP endpoint is unreachable, the OTLPMetricExporter's internal HTTP retry mechanism produces an OTLPExporterError: Export failed with retryable status as an unhandled promise rejection. This bypasses all existing try/catch layers (analytics.ts, FailSafeOtelService) because:

1. BaseOtelService.record() is synchronous — the export happens asynchronously via a detached forceFlush() call
2. The OTLP transport's retry logic rejects independently of the export() callback pattern
3. Node.js (v15+) treats unhandled promise rejections as uncaught exceptions, terminating the process

The existing .catch(() => {}) on forceFlush() only catches the InstantaneousMetricReader.onForceFlush() rejection, not the transport-level rejections from the HTTP exporter internals.

WHAT is this pull request doing?

Fixes the problem at the single chokepoint — InstantaneousMetricReader.onForceFlush():

1. Resolves instead of rejecting on export failure — metrics export is never fatal
2. Logs failures via diag.error() at the layer where the failure actually occurs
3. Removes the redundant .catch(() => {}) from BaseOtelService since forceFlush() can no longer reject
4. Adds tests for the InstantaneousMetricReader verifying it resolves on both success and failure

This makes all paths safe (forceFlush(), shutdown(), and any future callers) without needing scattered .catch() handlers.

How to test your changes?

npx vitest run packages/cli-kit/src/public/node/vendor/otel-js/export/InstantaneousMetricReader.test.ts
npx vitest run packages/cli-kit/src/private/node/otel-metrics.test.ts
npx vitest run packages/cli-kit/src/public/node/analytics.test.ts

Measuring impact

• n/a - bug fix for OTLP endpoint outage resilience

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes

🤖 Generated with Claude Code

[github-actions]

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If the changes are user-facing, run pnpm changeset add to track your changes and include them in the next release CHANGELOG.

Caution

DO NOT create changesets for features which you do not wish to be included in the public changelog of the next CLI release.

[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🟡	Statements	78.9%	14554/18447
🟡	Branches	73.22%	7222/9863
🟡	Functions	79.09%	3704/4683
🟡	Lines	79.25%	13761/17365

Test suite run success

3774 tests passing in 1455 suites.

Report generated by 🧪jest coverage report action from b8f39a0