feat: Add git-like diff and merge examples with professional color output

[zhangfengcdt]

This PR adds comprehensive examples demonstrating git-like tree diffing and merging workflows using
Prolly Trees, with professional color-coded terminal output for enhanced readability.

What's Added

🔍 Git Diff Example (examples/git_diff_example.rs)

• Realistic branching scenarios: Shows how trees evolve separately from a common root
• Three-way comparisons: main→feature, main→hotfix, and feature↔hotfix diffs
• Detailed analysis: File-level change tracking with additions, deletions, and modifications
• Git-like workflow: Simulates git diff main..feature style comparisons

🔀 Git Merge Example (examples/git_merge_example.rs)

• Fast-forward merge: When target branch is ahead of source
• Three-way merge: When both branches have diverged from common base
• Conflict resolution: Automatic detection and resolution of merge conflicts
• Professional strategies: Demonstrates real-world merge scenarios

🎨 Professional Terminal Output

• Semantic color coding:
  • 🟢 Green for success states and additions
  • 🔴 Red for conflicts and removals
  • 🔵 Blue for modifications and analysis
  • 🟡 Yellow for data and statistics
  • ⚫ Gray for secondary information
• No emoji dependency: Clean, accessible output suitable for all terminals
• Git-like aesthetics: Familiar formatting for developers

🔧 Technical Features

• Cryptographic verification: Each merge produces verifiable tree hashes
• Conflict detection: Identifies when same data is modified differently
• Merge strategies: Multiple approaches for different scenarios

Example Output

Diff Example

Git-like Tree Diffing Example

Creating main branch with initial data...
Main branch created with 5 files
Main tree hash: Some(ValueDigest([182, 243, 75, ...]))

Diff: main -> feature (shows what feature adds/changes)
Similar to: git diff main..feature
Changes: +0 files, -1 files, ~1 files modified

Merge Example

Scenario 3: Merge with conflicts
══════════════════════════════════════
Conflicts detected: 2 conflicts
Both modified: version.txt
Branch A: 1.1.0
Branch B: 1.0.1
Resolution: Using Branch A version
Conflicts resolved automatically!

🎯 Use Cases

• Version control systems: Demonstrate Prolly Tree capabilities for git-like workflows
• Distributed systems: Show efficient tree diffing and merging
• Data synchronization: Examples for conflict resolution strategies
• Educational: Clear demonstrations of Prolly Tree merge algorithms

Future Enhancements

Based on analysis, the core library could benefit from:

• Adding merge methods to the Tree trait
• Creating a dedicated merge module for standardized conflict resolution
• Enhancing diff functionality for three-way merge support

These examples demonstrate the foundation for such enhancements and provide a clear path forward for
integrating merge capabilities into the core Prolly Tree API.