fix(mcp): include collection name in status output (#416)

The MCP status tool shows collection paths but not names,
making it impossible for agents to discover valid collection
filter values. The CLI 'qmd status' already shows names.

Add col.name prefix to each collection line in the status
tool response.

src/mcp/server.ts

@@ -506,7 +506,7 @@ Intent-aware lex (C++ performance, not sports):
       ];
 
       for (const col of status.collections) {
-        summary.push(`    - ${col.path} (${col.documents} docs)`);
+        summary.push(`    - ${col.name}: ${col.path} (${col.documents} docs)`);
       }
 
       return {