refactor(examples): move example files to data/examples

Relocates all example YAML files from the `examples/` directory to `data/examples/`.
Updates `docs/schema-design.md` to reflect the new path for example files.

data/examples/plugin.yaml

@@ -0,0 +1,81 @@
+# Example Plugin Entry
+# Plugins are JS/TS modules that extend OpenCode's core functionality.
+# Place actual entries in: data/plugins/your-plugin-name.yaml
+
+# ============================================================================
+# REQUIRED FIELDS
+# ============================================================================
+
+name: Example Plugin
+repo: https://github.com/example/opencode-example-plugin
+tagline: A brief description of what this plugin does (max 120 chars)
+description: |
+  A longer description explaining the plugin in detail.
+  Can be multiple lines and include:
+  - Feature highlights
+  - Use cases
+  - Key benefits
+
+# ============================================================================
+# OPTIONAL FIELDS
+# ============================================================================
+
+# Scope defines where the extension can be installed (defaults to [global])
+# Most plugins work in both locations - omit or specify only what's relevant
+scope:
+  - global   # ~/.config/opencode/plugin/
+  - project  # .opencode/plugin/
+
+# Tags for filtering and discoverability
+tags:
+  - productivity
+  - ai
+  - authentication
+
+# Minimum OpenCode version required (semver format)
+min_version: "1.0.0"
+
+# Documentation URL if different from repository
+homepage: https://example.com/docs/opencode-plugin
+
+# Detailed installation instructions (markdown format)
+# Include sections relevant to your plugin
+installation: |
+  ## Prerequisites
+  - OpenCode 1.0.0 or later
+  - Node.js 18+ (for local development)
+
+  ## Installation
+
+  ### Global (all projects)
+  ```bash
+  # Clone to global plugins directory
+  git clone https://github.com/example/opencode-example-plugin ~/.config/opencode/plugin/example-plugin
+  ```
+
+  ### Project-only
+  ```bash
+  # Clone to project plugins directory
+  git clone https://github.com/example/opencode-example-plugin .opencode/plugin/example-plugin
+  ```
+
+  ## Configuration
+  Add to your `opencode.json`:
+  ```json
+  {
+    "plugins": {
+      "example-plugin": {
+        "enabled": true,
+        "option1": "value"
+      }
+    }
+  }
+  ```
+
+  ## Files Modified
+  - `~/.config/opencode/opencode.json` (config entry)
+  - `~/.config/opencode/plugin/example-plugin/` (plugin files)
+
+  ## Removal
+  1. Remove the plugin directory
+  2. Remove the config entry from `opencode.json`