Address feedback from @yinwm for long-running daemon use:
- Replace sync.Map with a fixed-size sharded lock array (64 mutexes).
Keys are mapped via FNV hash, so memory is O(1) regardless of how
many sessions are created over the process lifetime.
- Increase scanner buffer cap from 1 MB to 10 MB. Tool results
(read_file on large files, web search responses) can easily exceed
1 MB. The scanner still starts at 64 KB and only grows as needed.
Address review feedback from @Zhaoyikaiii:
- Replace map[string]*sync.Mutex + separate mu with sync.Map.LoadOrStore
for simpler, lock-free session lock management.
- Add skip parameter to readMessages so callers (GetHistory, Compact)
can skip truncated lines without paying the json.Unmarshal cost.
- Add countLines helper for TruncateHistory's count reconciliation,
avoiding full deserialization when only the line count is needed.
Address file growth concern from #711 review: logical truncation via
skip offset is fast but leaves dead lines on disk indefinitely.
Compact() rewrites the JSONL file keeping only active messages, using
the same temp+rename pattern for crash safety. No-op when skip == 0.
The caller (lifecycle manager or agent loop) decides when to trigger
compaction — e.g. when skipped lines exceed active lines.
Add JSONLStore that persists sessions as .jsonl files (one message per
line) plus .meta.json for summary and truncation offset.
Key design decisions:
- Append-only writes — no full-file rewrites on AddMessage
- Logical truncation via skip offset instead of physical deletion
- Per-session mutex for safe concurrent access
- Crash recovery: malformed trailing lines are silently skipped
- Atomic metadata writes using temp+rename
Zero new dependencies — pure stdlib.
Refs #711
