Port chatbot from C to Zig with comprehensive benchmarking

[vinitkumar]

This commit introduces a complete Zig implementation of the chatbot alongside
the original C version, with a focus on learning Zig and comparing the two
implementations.

Key Changes

Zig Implementation

• Implement hash table data structure with create, set, get, and destroy operations
• Port chatbot logic from C to Zig with proper memory management using allocators
• Add comprehensive test suite (5 tests covering hash table operations)
• Both C and Zig versions produce identical output for the same inputs

Project Structure

• Reorganize C and Zig implementations into separate directories:
  • c/: Original C implementation with Makefile
  • zig/: Zig port with build.zig configuration
• Add root-level README with building and testing instructions for both versions

CI/CD

• Add GitHub Actions workflow (.github/workflows/zig.yml) that:
  • Builds C version using gcc
  • Builds and tests Zig version (Zig 0.15.2)
  • Validates both executables run successfully

Benchmarking

• Add build-time benchmark (benchmark.sh) comparing compilation speed and binary size

  • C: 93ms build time, 33K executable
  • Zig: 710ms build time, 1.3M executable (C is 7.63x faster)

• Add runtime benchmark (run_benchmarks.sh) comparing execution performance

  • Builds both versions, runs with identical test inputs (test_inputs.txt)
  • Validates output equivalence between implementations
  • C: 286ms execution time, 1.83x faster than Zig

• Add BENCHMARK.md with detailed analysis of build metrics

Documentation

• Add zig/README.md with Zig-specific build and test instructions
• Update root README with:
  • Benchmarking results summary and tables
  • Instructions for running both build and runtime benchmarks
  • Building instructions for C and Zig versions separately

Build Artifacts

• Update .gitignore to exclude Zig build artifacts (.zig-cache/, zig-out/)

Testing & Validation

• All 5 Zig tests pass (hash table operations)
• Both C and Zig versions produce identical output for test inputs
• CI runs on both main and zig-port branches