Add managed system configuration and file changes

[david-kariuki]

Summary

Add a controlled framework for applying workstation configuration changes to system and user files safely, idempotently, and predictably.

Modules should use this framework rather than directly overwriting configuration files or embedding ad hoc file-editing commands.

Scope

• Provide shared utilities for managed configuration changes
• Support creating and updating configuration files
• Support controlled changes to existing configuration files
• Detect when the desired configuration is already present
• Avoid rewriting files when no change is required
• Perform file replacement atomically where practical
• Preserve or explicitly define file ownership and permissions
• Create backups before modifying existing files where appropriate
• Support system-level and user-level configuration files
• Integrate privileged file changes with the shared execution layer
• Integrate configuration actions with execution planning
• Support dry-run previews of intended configuration changes
• Avoid exposing sensitive configuration values in logs
• Provide clear failure handling for partial or unsuccessful writes

Acceptance Criteria

• Modules do not need to implement their own generic file-mutation logic
• Existing configuration is inspected before changes are applied
• Re-running the same configuration action is idempotent
• Existing files are not unnecessarily rewritten
• System-level configuration changes use controlled privilege escalation
• File ownership and permissions remain correct after changes
• Existing files can be backed up before potentially destructive modification
• Failed writes do not leave partially written configuration files where atomic replacement is possible
• Dry-run reports intended configuration changes without modifying files
• Sensitive values are not blindly written to session logs
• Configuration actions appear in the execution plan
• The framework can be tested using temporary files without changing the developer workstation