Add -y flag to npx to avoid first-install prompt hanging MCP connection

Without -y, npx prompts 'Ok to proceed? (y)' on first install of a
package, which hangs the stdio MCP connection (no TTY to answer).

Keeping version unpinned (auto-latest) — currently pulls 1.3.1 which
has the interact/annotation capabilities. Tested end-to-end via
'claude --plugin-dir pdf-viewer/'.

pdf-viewer/.mcp.json

@@ -2,7 +2,7 @@
   "mcpServers": {
     "pdf": {
       "command": "npx",
-      "args": ["@modelcontextprotocol/server-pdf", "--stdio"]
+      "args": ["-y", "@modelcontextprotocol/server-pdf", "--stdio"]
     }
   }
 }