feat(agent): migrate OpenCode 2 runtime and sandbox tools

Upgrade the runtime and native plugin API to OpenCode 2.0.24. Restore
session-scoped learning, credential renewal, typed project queries and
controlled frontend actions from the legacy Agent.

Replace host Shell execution with an approved Landlock/seccomp executor
and persistent per-session workspaces. Add typed Bocha search and Tianditu
geocoding bridges using the owning session credential. Require a working
kernel sandbox before startup and persist workspace files in deployments.

Validation completed before this commit: TypeScript checks, 150 Bun tests,
Docker build and UID 10001 sandbox execution, native Shell approval and
session recovery. Tianditu succeeded; Bocha currently reports exhausted
account quota. Unrelated investigation-report contract work is excluded.

.opencode/tjwater-plugin/index.ts

@@ -0,0 +1 @@
+export { default } from "../plugins/tjwater-tools.js";

.opencode/tjwater-plugin/package.json

@@ -0,0 +1,7 @@
+{
+  "name": "tjwater-tools-plugin",
+  "version": "1.0.0",
+  "private": true,
+  "type": "module",
+  "exports": "./index.ts"
+}