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Establish the nested persistence module — the architectural reason the core stays lean: a SEPARATE go.mod carrying modernc.org/sqlite (pure Go, no cgo), so the SQLite driver NEVER enters the executus core go.sum. A static-binary host (gadfly) importing only the core stays static; a host wanting turnkey persistence imports contrib/store. - sqlite.go: store.Open(dsn) -> *DB (one SQLite file), accessor-per-seam. - budget_store.go: db.Budget() satisfies budget.BudgetStorage; Add() does the 7-day window rollover atomically inside a transaction (concurrent Adds can't race the read-modify-write — the in-memory store's one weak spot). - Conformance test: budget.NewDBBudget over the SQLite store passes the SAME rolling-window contract as the in-memory store. - CI: a new step builds + tests contrib/store on its own AND asserts it carries the sqlite driver the core forbids (proof the split works). Verified: core go.sum has 0 sqlite refs; contrib/store go.sum has it. persona/skill/audit SQLite stores follow next (same JSON-blob + indexed-columns pattern, sidestepping the three-layer field-loss footgun). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>