Add ShellJS compatibility layer with 4 new streaming commands

[konard]

Summary

• ✅ Added 4 new streaming commands: head, tail, sort, uniq
• ✅ Exceeded ShellJS feature parity: Now have 25 built-in commands (vs ShellJS's 22)
• ✅ Added $.shelljs compatibility layer: Provides ShellJS-style API for migration
• ✅ Maintained streaming advantages: All new commands support real-time streaming, virtual command features, and async iteration
• ✅ Comprehensive testing: Added full test suite for all new functionality
• ✅ Version bump: Updated to 0.8.0 for this feature release

New Built-in Commands

head - Show first N lines (default: 10)

$`head -n 5 file.txt`     # First 5 lines
$`head -3 file.txt`       # First 3 lines (short format)

tail - Show last N lines (default: 10)

$`tail -n 5 file.txt`     # Last 5 lines
$`tail -3 file.txt`       # Last 3 lines (short format)

sort - Sort lines with options

$`sort file.txt`          # Alphabetical sort
$`sort -r file.txt`       # Reverse sort
$`sort -n file.txt`       # Numeric sort
$`sort -u file.txt`       # Sort with unique lines only

uniq - Remove consecutive duplicate lines

$`sort file.txt | uniq`       # Remove duplicates
$`sort file.txt | uniq -c`    # Count occurrences
$`sort file.txt | uniq -d`    # Show only duplicates
$`sort file.txt | uniq -u`    # Show only unique lines

ShellJS Compatibility Layer

Import and use the shelljs compatibility API:

import { $, shelljs } from 'command-stream';

// ShellJS-style API (async)
const result = await shelljs.head('-n', '5', 'file.txt');
console.log(result.stdout, result.code);

// Or continue using our streaming template literals (recommended)
const streamResult = await $`head -n 5 file.txt`;

Streaming Advantages Over ShellJS

• ✅ Real-time streaming vs ShellJS buffered output
• ✅ Virtual command engine vs ShellJS's static commands
• ✅ Mixed pipelines with both virtual and system commands
• ✅ EventEmitter pattern for advanced stream handling
• ✅ Async iteration support for processing large datasets
• ✅ Advanced signal handling for proper cleanup
• ✅ Template literal syntax vs function call syntax

Test Results

All tests passing:

• ✅ 16/16 new command tests pass
• ✅ 627/629 total tests pass (2 pre-existing failures unrelated to this PR)
• ✅ Full command compatibility verified

Command Count Comparison

Library	Built-in Commands
command-stream	25 ✅
ShellJS	22

New total: 25 commands now available, exceeding ShellJS by 3 commands.

Migration from ShellJS

Developers can now easily migrate from ShellJS while gaining our streaming advantages:

// Before (ShellJS)
import shell from 'shelljs';
const result = shell.head('-n', '5', 'file.txt');

// After (command-stream compatibility)
import { shelljs } from 'command-stream';
const result = await shelljs.head('-n', '5', 'file.txt');

// Or use our recommended streaming syntax
import { $ } from 'command-stream';
const result = await $`head -n 5 file.txt`;

Closes #25

🤖 Generated with Claude Code