fix: separate console streams for proper stdout/stderr routing (#255)

Create separate Console instances for regular CLI output (stdout) and
error handling (stderr). This ensures:
- Logo, help, and normal UI go to stdout (console)
- Error tracebacks and error messages go to stderr (err_console)

Author: pyq

src/mcpm/cli.py

@@ -7,6 +7,7 @@
 
 from rich.console import Console
 from rich.traceback import Traceback
+from rich.traceback import install as install_rich_traceback
 
 from mcpm.clients.client_config import ClientConfigManager
 from mcpm.commands import (
@@ -31,12 +32,17 @@
 from mcpm.utils.logging_config import setup_logging
 from mcpm.utils.rich_click_config import click, get_header_text
 
-console = Console()
+console = Console()          # stdout for regular CLI output
+err_console = Console(stderr=True)  # stderr for errors/tracebacks
 client_config_manager = ClientConfigManager()
 
 # Setup Rich logging early - this runs when the module is imported
 setup_logging()
 
+# Install Rich's global exception handler to use stderr instead of stdout
+# This prevents Rich/rich-gradient from routing tracebacks to stdout
+install_rich_traceback(console=err_console, show_locals=True)
+
 # Custom context settings to handle main command help specially
 CONTEXT_SETTINGS: Dict[str, Any] = dict(help_option_names=[])
 
@@ -53,9 +59,9 @@ def wrapper(*args, **kwargs):
         try:
             return func(*args, **kwargs)
         except Exception:
-            console.print(Traceback(show_locals=True))
-            console.print("[bold red]An unexpected error occurred.[/bold red]")
-            console.print(
+            err_console.print(Traceback(show_locals=True))
+            err_console.print("[bold red]An unexpected error occurred.[/bold red]")
+            err_console.print(
                 "Please report this issue on our GitHub repository: "
                 "[link=https://github.com/pathintegral-institute/mcpm.sh/issues]https://github.com/pathintegral-institute/mcpm.sh/issues[/link]"
             )