feat: metadata_assistant agent, tool call display, and agent selector UI

CHANGELOG.md

@@ -25,6 +25,27 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   absent, fixing the CI `@objectstack/client#test` failure.
 
 ### Added
+- **Metadata Assistant Agent (`service-ai`)** — New `metadata_assistant` agent definition that
+  binds all 6 metadata management tools (`create_object`, `add_field`, `modify_field`,
+  `delete_field`, `list_metadata_objects`, `describe_metadata_object`). Includes a tailored
+  system prompt that guides the AI to use snake_case naming, verify existing schemas before
+  modifications, and warn about destructive operations. Configured with `react` planning
+  strategy (10 iterations, replan enabled) for multi-step schema design conversations.
+- **Tool Confirmation Flags** — Added `requiresConfirmation: true` to `create_object` and
+  `delete_field` tool definitions. These destructive/creation operations now signal to the
+  frontend that user approval is needed before execution.
+- **Frontend Tool Call Display (`AiChatPanel`)** — Enhanced the AI Chat Panel to render tool
+  invocation parts from the Vercel AI SDK v6 stream protocol. Displays tool call status with
+  visual indicators:
+  - **Calling**: Spinner animation with tool name and argument summary
+  - **Confirmation**: Yellow-bordered card with Approve/Deny buttons for `requiresConfirmation` tools
+  - **Success**: Green success indicator with result preview
+  - **Error**: Red error indicator with error message
+  - **Denied**: Muted indicator for user-denied operations
+- **Operation Confirmation Mechanism** — Integrated the Vercel AI SDK `addToolApprovalResponse`
+  hook to support approval/denial workflows for tools marked with `requiresConfirmation`.
+  When the server sends an `approval-requested` state, the chat panel shows Approve and Deny
+  buttons. User decisions are sent back to the server to continue or abort the tool execution.
 - **Metadata Management Tools (`service-ai`)** — Added 6 built-in AI tools for metadata
   CRUD operations, each defined as a first-class `Tool` metadata file using `defineTool()`
   from `@objectstack/spec/ai`: