--headed fails on Linux: DISPLAY env var not passed to browser subprocess

Description

When using --headed mode on Linux with a virtual display (Xvnc, Xvfb), the browser fails to launch because the DISPLAY environment variable is not forwarded to the Chromium subprocess.

Steps to Reproduce

# Start virtual display
Xvnc :99 -geometry 1280x720 -depth 24 &
DISPLAY=:99 openbox &

# This fails
DISPLAY=:99 agent-browser open --headed https://example.com

Expected: Browser launches on display :99

Actual: Error "Missing X server or $DISPLAY"

✗ browserType.launch: Target page, context or browser has been closed

╔══════════════════════════════════════════════════════════════════════╗
║ Looks like you launched a headed browser without having a XServer    ║
║ running. Set either 'headless: true' or use 'xvfb-run'.              ║
╚══════════════════════════════════════════════════════════════════════╝

[pid][err] Missing X server or $DISPLAY
[pid][err] The platform failed to initialize. Exiting.

Root Cause

In dist/browser.js, Playwright's launch() is called without the env option:

// Line ~927
this.browser = await launcher.launch({
    headless: options.headless ?? true,
    executablePath: options.executablePath,
    args: options.args,
});

Without env, Playwright doesn't forward environment variables (including DISPLAY) to the browser subprocess.

Suggested Fix

Pass the environment to browser subprocess:

this.browser = await launcher.launch({
    headless: options.headless ?? true,
    executablePath: options.executablePath,
    args: options.args,
    env: { ...process.env },
});

Same change needed for launchPersistentContext() calls (~lines 897, 913).

Workaround

Launch Chrome manually with DISPLAY set and connect via CDP:

DISPLAY=:99 chrome --remote-debugging-port=9222 --no-sandbox &
agent-browser --cdp 9222 open https://example.com

Environment

• OS: Ubuntu 24.04
• agent-browser: v0.8.x (compiled binary)
• Display: TigerVNC (Xvnc) on :99
• Node.js: v24

Related Issues

• #155 (--headed not working in WSL/Ubuntu)
• #150 (no browser popup in headed mode)

Use Case

AI agents running in cloud VMs need headed mode for visual debugging via VNC/noVNC.

Inspect the browser launch calls in dist/browser.js around lines 897, 913, and 927, starting with the reported missing DISPLAY error. Verify the headed Linux reproduction with DISPLAY=:99 and check that the persistent-context and regular launch paths pass the environment through. Done means the browser starts on the requested virtual display without requiring the CDP workaround.