feat: add OpenCode CLI path override and settings UI

- Add opencodeBinary field to settings and persistence flow
- Introduce OpenCode CLI settings panel with Browse and Save actions

package.json

@@ -85,7 +85,7 @@
     "@ibm/plex": "^6.4.1",
     "@lezer/highlight": "^1.2.3",
     "@octokit/rest": "^22.0.1",
-    "@opencode-ai/sdk": "^1.1.48",
+    "@opencode-ai/sdk": "^1.1.52",
     "@radix-ui/react-collapsible": "^1.1.12",
     "@radix-ui/react-dialog": "^1.1.15",
     "@radix-ui/react-dropdown-menu": "^2.1.16",