## Why
SQLite log persistence needs visibility into batch size, write latency,
failures, and entries dropped before they reach the writer. Exporter
diagnostics must not feed back into the SQLite log sink and keep metric
exports active indefinitely.
## What changed
- Record write count, duration, batch bytes, entry count, largest-entry size,
and queue drops with bounded outcome tags.
- Add explicit byte histogram boundaries for log batch metrics.
- Filter OTLP transport noise and the benign unsolicited HTTP/2 PING warning
from SQLite log persistence to prevent export cycles while retaining other
HTTP/2 warnings.
## Testing
- Cover metric values, tags, queue-drop reasons, and histogram boundaries.
- Verify successful and failed OTLP HTTP and gRPC exports become idle instead
of generating recurring SQLite log-write metrics.
GitOrigin-RevId: a63224ae15945fe84adc977a8b7d55bb47a4de53
0b94751cc4