3 tests covering:
- logTelemetry writes JSONL with ts injected
- GSTACK_TELEMETRY_OFF=1 silences all events
- logTelemetry never throws on disk failures
Uses GSTACK_HOME env var to redirect writes to a tmp dir; the telemetry
module reads HOME lazily so test mutations take effect.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>