fix: isolate subprocess stdin and decouple startup to prevent MCP stdio deadlocks

- Set stdin=subprocess.DEVNULL across runtime, client, and utility subprocess calls to avoid hijacking the parent process's stdin.
- Run awake service initialization asynchronously on a daemon thread in MCP server startup.
- Redirect logger header printing to stderr to ensure stdio JSON-RPC purity.
- Add unit and lifecycle tests for MCP stdio protocol handshake and stdin isolation.

artemis/interfaces/cli/commands/mcp.py

@@ -19,6 +19,7 @@ import os
 from pathlib import Path
 import re
 import sys
+import threading
 import tomllib
 from typing import Annotated
 
@@ -724,7 +725,9 @@ def mcp_command(
         console.print(syntax)
         raise typer.Exit(0)
 
-    start_awake_service()
+    threading.Thread(
+        target=start_awake_service, daemon=True, name="artemis-awake-init"
+    ).start()
     try:
         st = server_type.lower()
         if st in ("agent", "mobile", "artemis", "default"):