feat(memory): add opt-in scoped memory tools

AGENTS.md

@@ -30,9 +30,14 @@
   modified files; preserve JSONC comments and unrelated configuration.
 - Keep state scoped by project/session. Do not introduce a mutable module-level
   store for user session data.
+- Optional memory uses `ctx.storage` with project/session-derived key prefixes;
+  it is disabled by default and never auto-captures or injects model context.
+- Memory expiry is lazy (on access), not a background cleanup task; storage is
+  not encrypted by this package.
 - Every imported ECC file must have source, revision, attribution, and hash
   recorded in `docs/PROVENANCE.md`.
-- Tests do not prove provider-backed agent behavior; report that separately.
+- Tests do not prove provider-backed agent behavior or persistence in a live
+  OpenCode profile; report those separately.
 - `npm test` compiles into ignored `dist/`; `npm pack --dry-run` runs the
   `prepack` build hook and therefore writes generated output.