fix(build): resolve TS2589 in server.ts and axios header type drift

package-lock.json is gitignored, so CI's fresh npm install resolves newer
zod/axios than long-lived local node_modules and surfaced two type errors
(same pair as upstream InstaWP#22, fix adapted to keep the tool
description argument):

- server.tool's generic resolves ShapeOutput<Args> against the SDK's z3|z4
  union schema type, exploding instantiation depth (TS2589); call through
  an explicitly-typed cast.
- axios headers['content-type'] is AxiosHeaderValue (can be null/number);
  narrow to string before normalizeMimeType.

Verified with tsc --noEmit against both a fresh npm install and the
existing local node_modules, plus a stdio protocol probe (164-byte
initialize, 43/43 tool descriptions intact).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: jack-arturo

src/server.ts

@@ -7,7 +7,6 @@ import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
 import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';
 import { allTools, toolHandlers } from './tools/index.js';
 import { z } from 'zod';
-import { zodToJsonSchema } from 'zod-to-json-schema';
 
 
 // Create MCP server instance.
@@ -43,8 +42,12 @@ for (const tool of allTools) {
 
     // Tool modules define inputSchema.properties as zod shapes (see CLAUDE.md);
     // passing raw JSON Schema here collapses the published schema to {}.
-    const zodSchema = z.object(tool.inputSchema.properties as z.ZodRawShape);
-    server.tool(tool.name, tool.description ?? '', zodSchema.shape, wrappedHandler)
+    const rawShape = tool.inputSchema.properties as z.ZodRawShape;
+    // Cast bypasses TS2589: server.tool's generic resolves ShapeOutput<Args>
+    // against the SDK's z3|z4 union schema type, exploding instantiation depth.
+    (server.tool as (name: string, description: string, schema: z.ZodRawShape, cb: typeof wrappedHandler) => unknown)(
+        tool.name, tool.description ?? '', rawShape, wrappedHandler
+    );
 
 }
 

src/tools/media.ts

@@ -255,7 +255,8 @@ async function loadUploadFromUrl(sourceUrl: string, explicitTitle?: string): Pro
   }
 
   const response = await axios.get<ArrayBuffer>(sourceUrl, { responseType: 'arraybuffer' });
-  const mimeType = normalizeMimeType(response.headers['content-type']);
+  const contentTypeHeader = response.headers['content-type'];
+  const mimeType = normalizeMimeType(typeof contentTypeHeader === 'string' ? contentTypeHeader : undefined);
   const originalFilename = deriveFilenameFromUrl(sourceUrl, mimeType);
   const filename = buildUploadFilename(originalFilename, explicitTitle);