Initial scaffold: open-memory plugin for OpenCode

- Plugin entry point with hooks: experimental.session.compacting,
  experimental.chat.system.transform, event
- Context tracker: SSE-based token tracking per session with
  green/yellow/red/critical thresholds
- Tools: memory_context, memory_compact, memory_summary,
  memory_sessions, memory_messages, memory_search, memory_plans
- History module: sqlite3 queries + markdown rendering
- Compaction: improved prompt emphasizing self-continuity
- Research docs: ARCHITECTURE.md + opencode-memory reference

biome.json

@@ -0,0 +1,20 @@
+{
+  "$schema": "https://biomejs.dev/schemas/2.3.11/schema.json",
+  "vcs": {
+    "enabled": true,
+    "clientKind": "git",
+    "useIgnoreFile": true
+  },
+  "formatter": {
+    "enabled": true,
+    "indentStyle": "space",
+    "indentWidth": 2,
+    "lineWidth": 100
+  },
+  "linter": {
+    "enabled": true,
+    "rules": {
+      "recommended": true
+    }
+  }
+}