fix: Prevent StdioTransport premature disconnection (Variant 1: stream_select + feof)

[ArtemYurov]

Problem:

• MCP server disconnects after ~60 seconds of inactivity
• fread() blocks and returns false when no data available
• This triggers "Failed to read from STDIN" error and breaks the listening loop

Solution (Variant 1):

• Use stream_select() with 1-second timeout to check data availability before reading
• Keep feof() check for maximum compatibility with different systems
• Enable graceful shutdown by checking $this->closing flag every second
• Prevents blocking while maintaining proper EOF detection

Testing:
✅ Tested for 150+ seconds without disconnections
✅ Compatible with macOS and other UNIX systems
✅ Graceful shutdown works correctly

Changes:

• Added stream_select() before fread() to wait for available data
• Short 1-second timeout allows periodic check of $this->closing flag
• Maintains feof() for EOF detection compatibility
• Fixed $deferred->resolve() to pass null argument (line 145)