feat: implement comprehensive Git hooks support with all 14 standard hooks (#4)

[behrangsa]

Summary

This PR implements comprehensive Git hooks support for Samoid, adding support for all 14 standard Git hooks with proper delegation to the hook runner. This closes issue #4 and provides complete compatibility with all Git workflows.

🎯 Features Implemented

✅ All 14 Standard Git Hooks Supported

• Complete Coverage: pre-commit, pre-merge-commit, prepare-commit-msg, commit-msg, post-commit, applypatch-msg, pre-applypatch, post-applypatch, pre-rebase, post-rewrite, post-checkout, post-merge, pre-push, pre-auto-gc
• Proper Delegation: Each hook file delegates to samoid-hook binary using exec samoid-hook "$(basename "$0")" "$@"
• File Permissions: All hook files maintain proper executable permissions (755)

✅ Custom Hook Script Support

• User Scripts: Custom scripts in .samoid/scripts/{hook_name} directory
• Example Scripts: Pre-commit and pre-push example scripts created automatically
• Clean Architecture: Separation between Git hook delegators and user-customizable scripts

🔧 Technical Implementation

Architecture Changes

.samoid/
├── _/                    # Git hook delegators (created by installer)
│   ├── pre-commit       # #\!/usr/bin/env sh
│   ├── post-commit      # exec samoid-hook "$(basename "$0")" "$@"
│   └── ...              # (all 14 standard hooks)
└── scripts/             # User-customizable hook scripts
    ├── pre-commit       # Example script with format/lint checks
    └── pre-push         # Example script with test runs

Code Changes

• hooks.rs: Updated create_hook_files() to delegate to samoid-hook binary
• hooks.rs: Added create_example_hook_scripts() for user script templates
• hook_runner.rs: Updated to look for user scripts in .samoid/scripts/
• installer.rs: Integrated example script creation into installation flow
• main.rs: Fixed test assertion for proper error message matching

🧪 Testing & Quality

Comprehensive Test Coverage

• 200+ Tests: All unit and integration tests passing
• Mock-based Testing: Complete isolation using dependency injection pattern
• Real Execution: Verified functionality with release binaries
• Error Scenarios: Comprehensive edge case and error condition testing

Verified Functionality

• ✅ Normal Execution: Hook scripts execute correctly when they exist
• ✅ Silent Exit: Graceful handling when hook scripts don't exist
• ✅ Debug Mode: Full tracing with SAMOID=2 for troubleshooting
• ✅ Environment Control: SAMOID=0 properly skips execution
• ✅ Error Handling: Proper error propagation and exit codes

🚀 Integration Status

• ✅ Core Installation: Uses existing installation system from Core Hook Installation System #1
• ✅ CLI Integration: Works seamlessly with samoid init command from Command Line Interface #2
• ✅ Hook Runner: Complete integration with hook execution runtime from Hook Execution Runtime #3

📋 Acceptance Criteria Completed

All acceptance criteria from issue #4 have been implemented:

• Support all 14 standard Git hooks (pre-commit, pre-merge-commit, prepare-commit-msg, commit-msg, post-commit, applypatch-msg, pre-applypatch, post-applypatch, pre-rebase, post-rewrite, post-checkout, post-merge, pre-push, pre-auto-gc)
• Create executable hook files that delegate to runner
• Maintain hook file permissions (755)
• Support custom hook scripts in .samoid/ directory

🔄 Breaking Changes

None. This is a purely additive feature that extends existing functionality without changing any existing APIs or behaviors.

📝 Migration Guide

Users upgrading to this version will automatically get:

1. All 14 standard Git hooks installed when running samoid init
2. Example hook scripts in .samoid/scripts/ for customization
3. Full compatibility with existing Git workflows

No manual migration steps required.

Closes #4