Add Chrome headless diagnostic tool

Runs automatically when --chrome-headless flag is used, checking:
- ChromeDriver installation and PATH
- Chrome/Chromium installation
- Chrome and ChromeDriver version compatibility
- config.toml chrome_binary setting
- Chrome for Testing installation
- ChromeDriver executable permissions (macOS quarantine)

Displays a detailed report with:
- Summary of detected versions and paths
- Pass/warning/error status for each check
- Specific fix suggestions for any issues found

Users can then ask g3 to help fix any detected issues.

Cargo.lock

@@ -1353,6 +1353,7 @@ dependencies = [
  "clap",
  "crossterm 0.29.0",
  "dirs 5.0.1",
+ "g3-computer-control",
  "g3-config",
  "g3-core",
  "g3-ensembles",
@@ -1386,6 +1387,7 @@ dependencies = [
  "cocoa 0.25.0",
  "core-foundation 0.10.1",
  "core-graphics 0.23.2",
+ "dirs 5.0.1",
  "fantoccini",
  "image",
  "objc",