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

src/history/queries.ts

@@ -0,0 +1,22 @@
+export const runQuery = async (dbUri: string, sql: string): Promise<Record<string, unknown>[]> => {
+  const proc = Bun.spawn(["sqlite3", "-json", dbUri, sql], {
+    stdout: "pipe",
+    stderr: "pipe",
+  });
+
+  const exitCode = await proc.exited;
+  const stdout = await new Response(proc.stdout).text();
+  const stderr = await new Response(proc.stderr).text();
+
+  if (exitCode !== 0) {
+    throw new Error(`sqlite3 exited with code ${exitCode}: ${stderr}`);
+  }
+
+  if (!stdout.trim()) return [];
+
+  try {
+    return JSON.parse(stdout) as Record<string, unknown>[];
+  } catch {
+    throw new Error(`Failed to parse sqlite3 output: ${stdout.slice(0, 200)}`);
+  }
+};