robobun d865ef41e2 feat: add Bun.Terminal API for pseudo-terminal (PTY) support (#25415)
## Summary

This PR adds a new `Bun.Terminal` API for creating and managing
pseudo-terminals (PTYs), enabling interactive terminal applications in
Bun.

### Features

- **Standalone Terminal**: Create PTYs directly with `new
Bun.Terminal(options)`
- **Spawn Integration**: Spawn processes with PTY attached via
`Bun.spawn({ terminal: options })`
- **Full PTY Control**: Write data, resize, set raw mode, and handle
callbacks

## Examples

### Basic Terminal with Spawn (Recommended)

```typescript
const proc = Bun.spawn(["bash"], {
  terminal: {
    cols: 80,
    rows: 24,
    data(terminal, data) {
      // Handle output from the terminal
      process.stdout.write(data);
    },
    exit(terminal, code, signal) {
      console.log(`Process exited with code ${code}`);
    },
  },
});

// Write commands to the terminal
proc.terminal.write("echo Hello from PTY!\n");
proc.terminal.write("exit\n");

await proc.exited;
proc.terminal.close();
```

### Interactive Shell

```typescript
// Create an interactive shell that mirrors to stdout
const proc = Bun.spawn(["bash", "-i"], {
  terminal: {
    cols: process.stdout.columns || 80,
    rows: process.stdout.rows || 24,
    data(term, data) {
      process.stdout.write(data);
    },
  },
});

// Forward stdin to the terminal
process.stdin.setRawMode(true);
for await (const chunk of process.stdin) {
  proc.terminal.write(chunk);
}
```

### Running Interactive Programs (vim, htop, etc.)

```typescript
const proc = Bun.spawn(["vim", "file.txt"], {
  terminal: {
    cols: process.stdout.columns,
    rows: process.stdout.rows,
    data(term, data) {
      process.stdout.write(data);
    },
  },
});

// Handle terminal resize
process.stdout.on("resize", () => {
  proc.terminal.resize(process.stdout.columns, process.stdout.rows);
});

// Forward input
process.stdin.setRawMode(true);
for await (const chunk of process.stdin) {
  proc.terminal.write(chunk);
}
```

### Capturing Colored Output

```typescript
const chunks: Uint8Array[] = [];

const proc = Bun.spawn(["ls", "--color=always"], {
  terminal: {
    data(term, data) {
      chunks.push(data);
    },
  },
});

await proc.exited;
proc.terminal.close();

// Output includes ANSI color codes
const output = Buffer.concat(chunks).toString();
console.log(output);
```

### Standalone Terminal (Advanced)

```typescript
const terminal = new Bun.Terminal({
  cols: 80,
  rows: 24,
  data(term, data) {
    console.log("Received:", data.toString());
  },
});

// Use terminal.stdin as the fd for child process stdio
const proc = Bun.spawn(["bash"], {
  stdin: terminal.stdin,
  stdout: terminal.stdin,
  stderr: terminal.stdin,
});

terminal.write("echo hello\n");

// Clean up
terminal.close();
```

### Testing TTY Detection

```typescript
const proc = Bun.spawn([
  "bun", "-e", 
  "console.log('isTTY:', process.stdout.isTTY)"
], {
  terminal: {},
});

// Output: isTTY: true
```

## API

### `Bun.spawn()` with `terminal` option

```typescript
const proc = Bun.spawn(cmd, {
  terminal: {
    cols?: number,        // Default: 80
    rows?: number,        // Default: 24  
    name?: string,        // Default: "xterm-256color"
    data?: (terminal: Terminal, data: Uint8Array) => void,
    exit?: (terminal: Terminal, code: number, signal: string | null) => void,
    drain?: (terminal: Terminal) => void,
  }
});

// Access the terminal
proc.terminal.write(data);
proc.terminal.resize(cols, rows);
proc.terminal.setRawMode(enabled);
proc.terminal.close();

// Note: proc.stdin, proc.stdout, proc.stderr return null when terminal is used
```

### `new Bun.Terminal(options)`

```typescript
const terminal = new Bun.Terminal({
  cols?: number,
  rows?: number,
  name?: string,
  data?: (terminal, data) => void,
  exit?: (terminal, code, signal) => void,
  drain?: (terminal) => void,
});

terminal.stdin;   // Slave fd (for child process)
terminal.stdout;  // Master fd (for reading)
terminal.closed;  // boolean
terminal.write(data);
terminal.resize(cols, rows);
terminal.setRawMode(enabled);
terminal.ref();
terminal.unref();
terminal.close();
await terminal[Symbol.asyncDispose]();
```

## Implementation Details

- Uses `openpty()` to create pseudo-terminal pairs
- Properly manages file descriptor lifecycle with reference counting
- Integrates with Bun's event loop via `BufferedReader` and
`StreamingWriter`
- Supports `await using` syntax for automatic cleanup
- POSIX only (Linux, macOS) - not available on Windows

## Test Results

- 80 tests passing
- Covers: construction, writing, reading, resize, raw mode, callbacks,
spawn integration, error handling, GC safety

## Changes

- `src/bun.js/api/bun/Terminal.zig` - Terminal implementation
- `src/bun.js/api/bun/Terminal.classes.ts` - Class definition for
codegen
- `src/bun.js/api/bun/subprocess.zig` - Added terminal field and getter
- `src/bun.js/api/bun/js_bun_spawn_bindings.zig` - Terminal option
parsing
- `src/bun.js/api/BunObject.classes.ts` - Terminal getter on Subprocess
- `packages/bun-types/bun.d.ts` - TypeScript types
- `docs/runtime/child-process.mdx` - Documentation
- `test/js/bun/terminal/terminal.test.ts` - Comprehensive tests

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>
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