feat(schema): refine and expand extension metadata schema

- Introduce `scope`, `tags`, `min_version`, `homepage`, and `installation` fields for enhanced discoverability and guidance.
- Remove `install` and `compatibility` objects, replacing them with a simplified `installation` string field.
- Add `examples/` directory with full exemplar files for each extension type.
- Update `schema-design.md` to reflect new schema, clarify field definitions, and improve documentation structure.

examples/resource.yaml

@@ -0,0 +1,80 @@
+# Example Resource Entry
+# Resources include guides, configs, MCP servers, tools, and commands.
+# Place actual entries in: data/resources/your-resource-name.yaml
+
+# ============================================================================
+# REQUIRED FIELDS
+# ============================================================================
+
+name: Example MCP Server
+repo: https://github.com/example/opencode-mcp-database
+tagline: MCP server for database access and querying
+description: |
+  A Model Context Protocol (MCP) server that provides
+  OpenCode with database access capabilities.
+  
+  Supports:
+  - PostgreSQL, MySQL, SQLite
+  - Read-only query execution
+  - Schema introspection
+
+# ============================================================================
+# OPTIONAL FIELDS
+# ============================================================================
+
+# Scope defines where the extension can be installed (defaults to [global])
+# For MCP servers, scope indicates global vs project-specific config
+scope:
+  - global   # System-wide MCP server
+  - project  # Project-specific database access
+
+tags:
+  - mcp-server
+  - database
+  - postgresql
+  - mysql
+
+min_version: "1.0.0"
+
+homepage: https://example.com/docs/mcp-database
+
+installation: |
+  ## Prerequisites
+  - Node.js 18+
+  - Database connection credentials
+
+  ## Installation
+  ```bash
+  # Install globally via npm
+  npm install -g @example/opencode-mcp-database
+  ```
+
+  ## Configuration
+  Add to your `opencode.json`:
+  ```json
+  {
+    "mcpServers": {
+      "database": {
+        "command": "opencode-mcp-database",
+        "args": ["--connection", "postgresql://localhost/mydb"]
+      }
+    }
+  }
+  ```
+
+  ## Environment Variables
+  Alternatively, configure via environment:
+  ```bash
+  export DATABASE_URL="postgresql://localhost/mydb"
+  ```
+
+  ## Security Notes
+  - Use read-only database credentials
+  - Consider connection pooling for production
+  - Review query permissions carefully
+
+  ## Removal
+  ```bash
+  npm uninstall -g @example/opencode-mcp-database
+  ```
+  Remove the `mcpServers.database` entry from `opencode.json`.