Add production-ready shell features: tab completion, aliases, history search, chaining, and redirection

[Copilot]

Transforms NShell from a basic shell into a feature-complete terminal with modern conveniences. Adds essential interactive features and advanced command execution capabilities.

New Built-in Commands (15 total)

• Navigation/Info: pwd, which, about
• Output: echo (with variable expansion), clear
• Shell Control: exit (saves history), help (shows all commands)
• Environment: export, unset, printenv
• Aliases: alias, unalias (persisted to ~/.nshell/nshellrc.json)
• History: history [n] command

Interactive Features

• Tab completion: Commands and file paths with multi-match display
• Ctrl+R: Reverse history search with interactive UI
• Ctrl+Left/Right: Word-based cursor navigation
• Command suggestions: Levenshtein distance-based "did you mean?" for typos

Advanced Command Execution

• Chaining: && (conditional), || (fallback), ; (sequential)
• Redirection: > (overwrite), >> (append)
• Piping: Basic | support between commands
• Alias expansion: Automatic substitution with persistence

Implementation Notes

• ConfigManager handles JSON persistence for aliases
• Enhanced KeyHandler with sophisticated binding system and tab completion logic
• CommandParser refactored with recursive execution for chaining, quote-aware splitting
• Levenshtein distance algorithm for smart command suggestions
• --no-banner flag for fast startup

Example usage:

# Persistent aliases
alias ll='ls -la'
ll

# Command chaining with redirection
echo "Building..." && dotnet build > build.log || echo "Failed!"

# History search
<Ctrl+R> # Interactive search

# Variable expansion
export MY_VAR="Hello"
echo {MY_VAR}

Stats: 24 files changed, 1,353 additions. Zero security issues (CodeQL verified). Zero build warnings.

Original prompt

Identify and suggest improvements, optimization, new features (original but useful ones to collect interest and stars on the project).

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[onihilist]

I just finished the fix on the PluginLoader, now you can add you own plugins !