refactor: split examples into separate packages and update Claude plan mode

- Restructure examples into individual packages per provider (daytona, docker, e2b, vercel) with shared utilities in @sandbox-agent/example-shared
- Make Claude plan mode prompt-only (no longer requires permissionMode=plan)
- Claude now defaults to bypass permission mode
- Add agent_file_edit_flow test for file editing capabilities
- Fix Daytona file permission setting to use executeCommand

examples/shared/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "@sandbox-agent/example-shared",
+  "private": true,
+  "type": "module",
+  "exports": {
+    ".": "./sandbox-agent-client.ts"
+  }
+}