fix: detect models that don't support image input and return clear error

Some models (Kimi K2, DeepSeek, Qwen text models) don't support image/vision
input. The AI SDK silently drops unsupported image parts, causing confusing
responses where the model acts as if no image was uploaded.

Added supportsImageInput() function to detect unsupported models by name,
and return a 400 error with clear guidance when users try to upload images
to these models.

Closes #469

packages/mcp-server/package-lock.json

@@ -1,18 +1,18 @@
 {
     "name": "@next-ai-drawio/mcp-server",
-    "version": "0.1.10",
+    "version": "0.1.6",
     "lockfileVersion": 3,
     "requires": true,
     "packages": {
         "": {
             "name": "@next-ai-drawio/mcp-server",
-            "version": "0.1.10",
+            "version": "0.1.6",
             "license": "Apache-2.0",
             "dependencies": {
                 "@modelcontextprotocol/sdk": "^1.0.4",
                 "linkedom": "^0.18.0",
                 "open": "^11.0.0",
-                "zod": "^4.0.0"
+                "zod": "^3.24.0"
             },
             "bin": {
                 "next-ai-drawio-mcp": "dist/index.js"
@@ -2051,9 +2051,9 @@
             }
         },
         "node_modules/zod": {
-            "version": "4.3.2",
-            "resolved": "https://registry.npmjs.org/zod/-/zod-4.3.2.tgz",
-            "integrity": "sha512-b8L8yn4rIVfiXyHAmnr52/ZEpDumlT0bmxiq3Ws1ybrinhflGpt12Hvv54kYnEsGPRs6o/Ka3/ppA2OWY21IVg==",
+            "version": "3.25.76",
+            "resolved": "https://registry.npmjs.org/zod/-/zod-3.25.76.tgz",
+            "integrity": "sha512-gzUt/qt81nXsFGKIFcC3YnfEAx5NkunCfnDlvuBSSFS02bcXu4Lmea0AFIUwbLWxWPx3d9p8S5QoaujKcNQxcQ==",
             "license": "MIT",
             "peer": true,
             "funding": {

packages/mcp-server/package.json

@@ -39,7 +39,7 @@
         "@modelcontextprotocol/sdk": "^1.0.4",
         "linkedom": "^0.18.0",
         "open": "^11.0.0",
-        "zod": "^4.0.0"
+        "zod": "^3.24.0"
     },
     "devDependencies": {
         "@types/node": "^24.0.0",