Add system dependencies support for tools

Tools can now declare system-level package dependencies (apt, brew, pacman, dnf)
that get checked and optionally installed when the tool is installed or run.

Features:
- SystemDependency dataclass with short form (string) and long form (dict)
- New system_deps.py module with platform detection and installation
- `cmdforge system-deps <tool>` command to check/install system packages
- `cmdforge check` now shows both CmdForge and system dependencies
- `cmdforge registry install` prompts for system dep installation
- GUI: System Dependencies section in Tool Builder with add/edit dialog
- Runner warns about missing system deps before execution
- Integration with project install (manifest and lock-based)

Also includes:
- Quote paths in wrapper scripts for spaces support
- Tests for value type preservation in code steps
- Unskip invalid tool name test

Co-Authored-By: Claude Opus 4.5 <[email protected]>

CHANGELOG.md

@@ -6,6 +6,49 @@ All notable changes to CmdForge will be documented in this file.
 
 ### Added
 
+#### System Dependencies
+- **System package dependencies for tools**: Tools can now declare system-level package dependencies (apt, brew, pacman, dnf)
+  - `system_dependencies` field in tool config.yaml
+  - Short form: just package name (e.g., `ffmpeg`)
+  - Long form: detailed spec with description, binaries to check, and per-manager package names
+  - Automatic platform detection (Linux/macOS/Windows)
+  - Package manager detection (apt, brew, pacman, dnf)
+
+- **New dataclass**: `SystemDependency` in tool.py
+  - `name` - Package identifier
+  - `description` - Why this dependency is needed
+  - `binaries` - List of executables to check (defaults to [name])
+  - `packages` - Package names per manager (defaults to name for all)
+  - Round-trip serialization preserves short/long form
+
+- **New module**: `src/cmdforge/system_deps.py`
+  - `detect_os()` - Returns 'linux', 'darwin', or 'windows'
+  - `detect_package_manager()` - Returns 'apt', 'brew', 'pacman', 'dnf', or None
+  - `check_system_dep()` - Check if dependency is satisfied (any binary found)
+  - `install_system_dep()` - Install via system package manager
+  - `prompt_install_missing()` - Interactive prompt for installing missing packages
+
+- **New CLI command**: `cmdforge system-deps <tool> [install]`
+  - `cmdforge system-deps <tool>` - Show system dependency status
+  - `cmdforge system-deps <tool> install` - Install missing system packages
+  - `--yes` flag for non-interactive installation
+
+- **Enhanced CLI commands**:
+  - `cmdforge check <tool>` - Now shows both CmdForge and system dependencies
+  - `cmdforge registry install` - Prompts to install system deps after tool install
+    - `--yes` flag to auto-install without prompting
+    - `--no-system-deps` flag to skip system dependency handling
+  - `cmdforge install` (project) - Handles system deps for manifest and lock-based installs
+
+- **GUI support**:
+  - Tool Builder: New "System Dependencies" section
+  - Add/Edit/Remove system dependency dialog
+  - Shows name and description in list
+
+- **Runtime integration**:
+  - Runner warns about missing system dependencies before execution
+  - Uses qualified tool refs (owner/name) for registry-installed tools
+
 #### Tool Settings Files
 - **Configurable tool settings**: Tools can now ship with default settings that users can customize
   - `defaults.yaml` - Default settings published with the tool (immutable)