fix(mcp): restore Content-Length framing for MCP stdio

Revert to LSP-style Content-Length framing for MCP stdio transport. Testing confirmed that MCP clients (Claude Code) do expect Content-Length headers, not raw NDJSON. The earlier NDJSON change was based on incorrect assumption about the protocol.

main.go

@@ -246,10 +246,7 @@ func writeResponse(resp interface{}) {
 }
 
 func writeFramed(data []byte) {
-	// MCP stdio transport uses newline-delimited JSON (NDJSON), not LSP-style
-	// Content-Length framing. Claude Code and other MCP clients reject
-	// Content-Length headers on stdio, so we emit one JSON object per line.
-	fmt.Fprintf(os.Stdout, "%s\n", data)
+	fmt.Fprintf(os.Stdout, "Content-Length: %d\r\n\r\n%s", len(data), data)
 }
 
 func debugLog(format string, args ...interface{}) {