Queries compaction-type parts in the DB to find session compaction
events, then retrieves the summary text from the adjacent assistant
message. Presents compactions as navigable checkpoints with list and
read modes.
Rewrites history/queries.ts to use bun:sqlite with readonly mode and
parameterized queries instead of spawning sqlite3. Consolidates threshold
constants into a single source of truth. Adds AGENTS.md as the canonical
operational doc, moves architecture to docs/, and adds initial test suite.
