#6865: fix: handle extended "fetch failed" messages in Node v25+

## Summary Handle extended "fetch failed" error messages in Node v25+ to prevent false-positive crash reports. **Problem**: Node v25 changed `fetch()` error messages from `"fetch failed"` to `"fetch failed: <details>"`. Existing detection logic uses exact string match and misses these. **Fix**: Use `startsWith("fetch failed")` instead of equality check. ## Risk Summary - **Severity**: Low (crash detection false positive, not a security issue) - **Regression risk**: None — strictly widens the match, no false negatives introduced - **Scope**: 2 files, +7/-1 lines ## Verification - [x] `pnpm build` passes - [x] `pnpm lint` passes - [x] `pnpm test` passes ## Sign-Off - Models used: Claude Opus 4.6 - Submitter effort: Verified Node v25 changelog for fetch error message format change, confirmed startsWith covers both old and new formats - Agent notes: N/A lobster-biscuit