docs(examples): Add README for debug-server

Author: ochafik

examples/debug-server/README.md

@@ -0,0 +1,55 @@
+# Debug Server
+
+A comprehensive testing/debugging tool for the MCP Apps SDK that exercises every capability, callback, and result format combination.
+
+## Tools
+
+### debug-tool
+
+Configurable tool for testing all result variations:
+
+| Parameter | Type | Default | Description |
+|-----------|------|---------|-------------|
+| `contentType` | `"text"` \| `"image"` \| `"audio"` \| `"resource"` \| `"resourceLink"` \| `"mixed"` | `"text"` | Content block type to return |
+| `multipleBlocks` | boolean | `false` | Return 3 content blocks |
+| `includeStructuredContent` | boolean | `true` | Include structuredContent in result |
+| `includeMeta` | boolean | `false` | Include _meta in result |
+| `largeInput` | string | - | Large text input (tests tool-input-partial) |
+| `simulateError` | boolean | `false` | Return isError: true |
+| `delayMs` | number | - | Delay before response (ms) |
+
+### debug-refresh
+
+App-only tool (hidden from model) for polling server state. Returns current timestamp and call counter.
+
+## App UI
+
+The debug app provides a dashboard with:
+
+- **Event Log**: Real-time log of all SDK events with filtering
+- **Host Info**: Context, capabilities, container dimensions, styles
+- **Callback Status**: Table of all callbacks with call counts
+- **Actions**: Buttons to test every SDK method:
+  - Send messages (text/image)
+  - Logging (debug/info/warning/error)
+  - Model context updates
+  - Display mode requests
+  - Link opening
+  - Resize controls
+  - Server tool calls
+  - File operations
+
+## Usage
+
+```bash
+# Build
+npm run --workspace examples/debug-server build
+
+# Run standalone
+npm run --workspace examples/debug-server serve
+
+# Run with all examples
+npm start
+```
+
+Then open `http://localhost:8080/basic-host/` and select "Debug MCP App Server" from the dropdown.