feat(core): add Pydantic models for wizard configuration (CLI-5)

Implements CLI-5: Complete Pydantic model structure for wizard system.

Models Added:

Action Types (Discriminated Union):
- BashActionConfig: Bash command execution with env variables
- PythonActionConfig: Python function invocation
- ActionConfigUnion: Type-safe discriminated union

Option Types (Discriminated Union):
- StringOptionConfig: Text input
- SelectOptionConfig: Dropdown/menu selection
- PathOptionConfig: File/directory path input
- NumberOptionConfig: Numeric input with min/max
- BooleanOptionConfig: Yes/no toggle
- OptionConfigUnion: Type-safe discriminated union

Navigation & Structure:
- MenuConfig: Navigation menu items
- BranchConfig: Wizard screen/step with actions, options, menus
- WizardConfig: Complete wizard with entry point and branches

State Management:
- SessionState: Unified state for wizard and parser
  - Current branch tracking
  - Navigation history
  - Option values
  - Variables for interpolation
  - Parser state (mode, command history)

Result Types:
- ActionResult: Action execution results
- CollectionResult: Option collection results
- NavigationResult: Navigation operation results

Features:
- StrictModel base class with Pydantic v2 strict mode
- Field validation with descriptive error messages
- JSON serialization/deserialization support
- Metadata and tagging infrastructure
- MyPy strict mode compliance

Tests: 159 unit tests covering all models and validation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: dugshub