feat: add per-project config file support for unsafe branches

[ericanderson]

Summary

Implements per-project configuration file support for customizing branch safety rules, resolving issue #17.

Key Features

• Custom Protected Branches: Override default protected branch lists
• Additional Protected Patterns: Add regex patterns to protect specific branch naming conventions
• Configurable Safety Rules: Control unpushed commit handling and merged PR requirements
• Custom Safety Rules: Define project-specific protection rules with custom error messages

Configuration File Discovery

Searches for configuration files in order of precedence:

1. Environment variable: GHOULS_CONFIG=/path/to/config.json
2. Repository root: .ghouls.json, .ghoulsrc.json, ghouls.config.json
3. User home: ~/.config/ghouls/config.json

Implementation Details

• New Types: SafetyConfig, GhoulsConfig interfaces with comprehensive validation
• Configuration Loading: Robust file discovery, JSON parsing, and error handling
• Safety Check Updates: Extended isBranchSafeToDelete() and filterSafeBranches() to support configuration
• Backward Compatibility: All existing behavior preserved when no config file present
• Comprehensive Testing: 69 new unit tests covering all configuration scenarios

Example Configuration

{
  "version": "1.0",
  "safety": {
    "protectedBranches": ["main", "develop", "staging", "production"],
    "additionalProtectedPatterns": ["release/.*", "hotfix/.*"],
    "allowUnpushedCommits": false,
    "requireMergedPR": true,
    "customSafetyRules": [
      {
        "name": "temp-branches",
        "pattern": "temp/.*",
        "reason": "temporary experiment branch"
      }
    ]
  }
}

Test Plan

• [✅] All existing tests pass (backward compatibility verified)
• [✅] 69 new unit tests covering configuration functionality
• [✅] TypeScript compilation passes without errors
• [✅] Configuration validation with error handling
• [✅] File discovery and loading edge cases
• [✅] Integration with existing safety check logic

🤖 Generated with Claude Code

[ericanderson]

config file in repo should be .config/ghouls.json