feat(service-ai): add runtime metadata tool handlers with registerMetadataTools()

Implement actual ToolHandler functions for all 6 metadata management
tools in packages/services/service-ai/src/tools/metadata-tools.ts:

- create_object: Validates snake_case name, checks duplicates, registers via IMetadataService
- add_field: Validates object exists, field doesn't exist, merges into object definition
- modify_field: Validates object/field exist, applies partial patch
- delete_field: Validates object/field exist, removes field from definition
- list_objects: Returns summaries with optional filter and field inclusion
- describe_object: Returns full schema with field array and feature flags

registerMetadataTools() follows same pattern as registerDataTools().
29 unit tests covering handler execution, validation, error paths,
and full create→add→modify→delete→describe lifecycle.

Agent-Logs-Url: https://github.com/objectstack-ai/spec/sessions/ff28e788-07bc-4fd3-99b2-9f6db7352c67

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

CHANGELOG.md

@@ -17,12 +17,16 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 - **Metadata Management Tools & Skill (Tool→Skill→Agent)** — Added 6 platform built-in AI
   tools for metadata operations (`create_object`, `add_field`, `modify_field`, `delete_field`,
-  `list_objects`, `describe_object`) in `packages/spec/src/ai/metadata-tools.zod.ts`. Each
-  tool has structured JSON Schema parameters, output schema, permission controls, and
-  confirmation requirements for destructive operations. Aggregated into `metadata_management`
-  skill in `metadata-skill.zod.ts` with trigger phrases and programmatic activation conditions.
-  Fully testable with 26 unit tests covering individual tool definitions, schema validation,
-  aggregate exports, and skill structure.
+  `list_objects`, `describe_object`):
+  - **Protocol definitions** in `packages/spec/src/ai/metadata-tools.zod.ts` and
+    `metadata-skill.zod.ts` — Zod-validated tool schemas with JSON Schema parameters,
+    output schemas, permission controls, and `metadata_management` skill aggregation.
+  - **Runtime implementation** in `packages/services/service-ai/src/tools/metadata-tools.ts` —
+    Actual `ToolHandler` functions that call `IMetadataService` CRUD methods (`register`,
+    `getObject`, `listObjects`) to create objects, add/modify/delete fields, and inspect
+    schemas. Registered via `registerMetadataTools(registry, { metadataService })`.
+  - 55 unit tests across spec (26) and service-ai (29) covering schema validation, handler
+    execution, error handling, full create→add→modify→delete lifecycle, and edge cases.
 - **Agent Skills — `skills/` directory (agentskills.io)** — Created `skills/` folder at
   repository root following the [agentskills.io specification](https://agentskills.io/specification).
   Five expert-knowledge skills with hand-written `SKILL.md` files and `references/` quick-lookup

ROADMAP.md

@@ -663,7 +663,7 @@ Objects now declare `namespace: 'sys'` and a short `name` (e.g., `name: 'user'`)
 - [ ] Agent runtime — execute AI agents defined in spec schemas
 - [x] Tool registry — connect agents to ObjectQL operations, APIs, and workflows (initial implementation in `service-ai`)
 - [x] Conversation management — persistent chat with context windows (initial implementation in `service-ai`)
-- [x] Metadata management tools — 6 built-in tools (`create_object`, `add_field`, `modify_field`, `delete_field`, `list_objects`, `describe_object`) with structured parameters, permissions, and `metadata_management` skill
+- [x] Metadata management tools — 6 built-in tools (`create_object`, `add_field`, `modify_field`, `delete_field`, `list_objects`, `describe_object`) with protocol definitions (`@objectstack/spec`) and runtime handlers (`@objectstack/service-ai`) registered via `registerMetadataTools()`
 
 ### 7.3 RAG Pipeline