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

REQUIREMENTS.md

@@ -26,3 +26,16 @@
 - Verify plugin activation and tool execution on OpenCode 2.0.24 using a local
   mock OpenAI-compatible endpoint; do not make a paid or remote provider call as
   part of deterministic validation.
+
+## Optional memory
+
+- Memory tools must not register unless explicitly enabled in plugin options.
+- Session memory is scoped to the current OpenCode project and session; project
+  memory is separately opt-in and shared only within the same canonical project.
+- Memory must be written, listed, retrieved, and deleted only through explicit
+  tool calls; prompts, tool outputs, and summaries are not captured automatically.
+- Apply a configurable expiration (default 30 days); expired entries must never
+  be returned, and memory content must not be automatically injected into future
+  model context or uploaded by the plugin.
+- Reject memory operations for sessions belonging to another project. Provider-
+  backed learning and live-profile persistence require separate verification.