Refactor: Centralize command patterns in single source of truth

CRITICAL: Prevents inconsistent sudo/SSH patterns across codebase.

Created command_patterns.py with:
- Single source of truth for ALL command execution patterns
- SSH key path constant: /var/lib/macha/.ssh/id_ed25519
- Remote user constant: macha
- sudo prefix for all remote commands
- Helper functions: build_ssh_command(), transform_ssh_command()
- Self-validation tests

Updated files to use centralized patterns:
- tools.py: Uses transform_ssh_command()
- remote_monitor.py: Uses build_ssh_command()
- system_discovery.py: Uses build_ssh_command()
- DESIGN.md: Documents centralized approach

Benefits:
- Impossible to have inconsistent patterns
- Single place to update if needed
- Self-documenting with validation tests
- Prevents future refactoring errors

DO NOT duplicate these patterns in other files - always import.

tools.py

@@ -8,6 +8,7 @@ import json
 import os
 from typing import Dict, Any, List, Optional
 from pathlib import Path
+from command_patterns import transform_ssh_command
 
 
 class SysadminTools:
@@ -268,21 +269,9 @@ class SysadminTools:
                     "allowed_commands": self.allowed_commands
                 }
         
-        # Automatically configure SSH commands to use macha user on remote systems
-        # Transform: ssh hostname cmd -> ssh -i /var/lib/macha/.ssh/id_ed25519 macha@hostname sudo cmd
-        if command.strip().startswith('ssh ') and '@' not in command.split()[1]:
-            parts = command.split(maxsplit=2)
-            if len(parts) >= 2:
-                hostname = parts[1]
-                remaining = ' '.join(parts[2:]) if len(parts) > 2 else ''
-                # Always use explicit SSH key path
-                ssh_key = "/var/lib/macha/.ssh/id_ed25519"
-                ssh_opts = f"-i {ssh_key} -o StrictHostKeyChecking=no"
-                # If there's a command to run remotely, prefix it with sudo
-                if remaining:
-                    command = f"ssh {ssh_opts} macha@{hostname} sudo {remaining}".strip()
-                else:
-                    command = f"ssh {ssh_opts} macha@{hostname}".strip()
+        # Automatically configure SSH commands using centralized command_patterns
+        # See command_patterns.py for the single source of truth
+        command = transform_ssh_command(command)
         
         try:
             result = subprocess.run(