Document singular metadata type naming convention

Agent-Logs-Url: https://github.com/objectstack-ai/framework/sessions/4b4cd0a2-3590-43af-8b11-0e6b59c0e99a

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

Co-authored-by: xuyushun441-sys <255036401+xuyushun441-sys@users.noreply.github.com>

Author: Claude

.github/copilot-instructions.md

@@ -15,6 +15,8 @@
 3. **Naming Convention:**
     - **Configuration Keys (TS Props):** `camelCase` — e.g., `maxLength`, `referenceFilters`, `defaultValue`.
     - **Machine Names (Data Values):** `snake_case` — e.g., `name: 'first_name'`, `object: 'project_task'`.
+    - **Metadata Type Names:** `singular` — e.g., `'agent'`, `'tool'`, `'view'`, `'flow'` (NOT `'agents'`, `'tools'`, `'views'`, `'flows'`). This aligns with the canonical `MetadataTypeSchema` enum in `packages/spec/src/kernel/metadata-plugin.zod.ts`.
+    - **REST API Endpoints:** `plural` — e.g., `/api/v1/ai/agents`, `/api/v1/ai/conversations` (per REST convention for resource collections).
 4. **Namespace Imports:** Use `import { Data, UI, System } from '@objectstack/spec'` or subpath `import { Field } from '@objectstack/spec/data'`. Never use relative paths like `../../packages/spec`.
 5. **Best Practice Mandate:**
     - Benchmark against industry leaders (Salesforce, ServiceNow, Kubernetes) for structural decisions.

packages/spec/src/kernel/metadata-plugin.zod.ts

@@ -52,6 +52,20 @@ import { MergeStrategyConfigSchema, CustomizationPolicySchema } from './metadata
  * The canonical list of all metadata types managed by the platform.
  * Each type maps to a specific Zod schema (e.g., ObjectSchema, ViewSchema).
  * Plugins can extend this registry via `contributes.kinds` in the manifest.
+ *
+ * ## Naming Convention
+ * **IMPORTANT:** All metadata type names are in **SINGULAR** form:
+ * - ✅ Use: `'agent'`, `'tool'`, `'skill'`, `'view'`, `'flow'`, `'action'`
+ * - ❌ NOT: `'agents'`, `'tools'`, `'skills'`, `'views'`, `'flows'`, `'actions'`
+ *
+ * This convention applies to:
+ * - Protocol definitions (this enum)
+ * - UI plugin registrations (`metadataTypes`, `metadataIcons`)
+ * - Metadata service operations
+ * - File patterns (`*.agent.ts`, `*.tool.ts`)
+ *
+ * REST API endpoints continue to use plural forms per REST conventions:
+ * - `/api/v1/ai/agents`, `/api/v1/ai/conversations`
  */
 export const MetadataTypeSchema = z.enum([
   // Data Protocol