Add Shell Auto-Completion Support

Description

Add shell auto-completion scripts for bash, zsh, and fish to improve developer experience and command discoverability. Users should be able to tab-complete commands, options, testset names, solution names, and other context-aware arguments.

Features

Command Completion:

polyman gen<TAB>  → polyman generate
polyman rem<TAB>  → polyman remote

Option Completion:

polyman generate --<TAB>
→ --all  --testset  --group  --index

polyman remote push --<TAB>
→ --all  --solutions  --checker  --validator  --tests

Context-Aware Completion:

# Complete testset names from Config.json
polyman generate -t <TAB>
→ tests  samples  pretests

# Complete solution names from Config.json
polyman run <TAB>
→ main  correct2  wa-solution  tle-solution

# Complete generator names
polyman generate -t tests -g <TAB>
→ samples  main  stress

Implementation Approach Using commander-completion

import completion from 'commander-completion';

program
  .command('completion')
  .description('Generate shell completion script')
  .action(() => {
    completion(program);
  });

Success Criteria

• Completion works for all shells (bash, zsh, fish)
• Static command/option completion works
• Dynamic completion reads Config.json
• Handles missing Config.json gracefully (fallback to static completion)
• Installation instructions in README
• Auto-suggest during npm install -g polyman-cli