fix(filesystem): move_file outputSchema returns array not string

[haroldfabla2-hue]

Summary

Fixes #3093

Problem

The move_file tool's outputSchema incorrectly declares content: z.string() but the handler returns content: [contentBlock] (an array). This mismatch causes MCP protocol validation to fail with error -32602:

Output validation error: Invalid structured content for tool move_file:
  expected string, received array

Fix

Changed outputSchema from:

outputSchema: { content: z.string() }

to:

outputSchema: { content: z.array(z.object({ type: z.string(), text: z.string() })) }

This matches the actual return value:

return {
  content: [contentBlock],  // array of {type: 'text', text: string}
  structuredContent: { content: text }
};

Testing

The bug was reported by a user on Windows 10 with Claude Desktop 1.0.130.7 and @modelcontextprotocol/server-filesystem@latest. The fix aligns the schema declaration with the actual runtime behavior.