# SQ-017: WAL Trimming

**Status:** `[x] DONE`
**Blocked by:** SQ-016
**Priority:** Medium

## Description

Garbage collect local WAL segments after they have been confirmed in object storage.

## Files to Create/Modify

- `crates/sq-storage/src/wal/trimmer.rs` - WalTrimmer

## Behavior

1. Periodically scan for segments marked as "shipped"
2. Verify the segment exists in object storage (optional double-check)
3. Delete the local WAL segment file
4. Update the offset index to point to S3 location instead

## Acceptance Criteria

- [ ] Segment marked as shipped -> trimmer deletes local file
- [ ] Segment NOT marked as shipped -> trimmer leaves it
- [ ] After trimming, index entries point to S3 location
- [ ] Trimmer respects a minimum retention period (keep recent segments locally even if shipped)