Introduce scripts/persist.ts — the single, provider- and binding-agnostic
layer that consumes an adapter's IndexRecord stream and writes rows into an
injected SQLite handle (node:sqlite for skill/CLI, better-sqlite3 for the app).
It is the only layer that touches the database.
Write semantics are the canonical ones reconciled from the earlier drift:
- messages upsert via ON CONFLICT (turn_duration_ms not in the column list, so
it is never clobbered)
- sessions merge with the existing row: started_at MIN, ended_at MAX,
message_count reset-or-accumulate by resume state, fill-if-null for the rest;
project_path is preserved and left to refreshSessionProjectPaths
- message-turn-duration applies as a targeted UPDATE
- delete-session cascades across all tables
- the generator's return cursor is written back to index_state (mtime:lines →
the two existing columns; no schema migration yet)
Purely additive — buildIndex still uses the old indexJsonl path, so existing
behavior is unchanged. Rewiring happens in 5b-2b.
Adds tests/persist.test.mjs: all record kinds written, resume does not
double-count message_count, fresh re-scan resets it, delete-session cascades.
Full suite 115/115, lint + typecheck green.
