feat: MCP-created minesweeper plugin + fix callCreatePlugin mode field

- Minesweeper: 8×8 grid, 10 mines, fullscreen Canvas game
  - Tap to reveal, long-press 400ms to flag
  - First click safe (mines placed after first reveal)
  - Flood-fill on zero cells
  - Win detection + celebration melody
  - Audio feedback (tone per adjacent mine count)
- Fixed callCreatePlugin: now parses 'mode' field (was hardcoded to inline)

Co-Authored-By: Claude <noreply@anthropic.com>

app/src/main/java/com/nonvioce/ijs/McpServer.java

@@ -536,6 +536,7 @@ public class McpServer extends NanoHTTPD {
         plugin.put("name", args.getString("name"));
         plugin.put("icon", args.optString("icon", "🔌"));
         plugin.put("command", args.optString("command", ""));
+        plugin.put("mode", args.optString("mode", "inline"));
         plugin.put("description", args.optString("description", ""));
 
         // js_code from MCP params → jsCode in plugin JSON