fix: Don't advertise IDLE until ChromeDriver is validated at startup

[aaronkvanmeerten]

Summary

• Jibri was broadcasting IDLE+HEALTHY to XMPP MUCs immediately on startup before ChromeDriver was validated, allowing Jicofo to dispatch requests that would fail during ChromeDriver initialization
• Adds an EnvironmentChecker that registers as UNHEALTHY at construction, then probes ChromeDriver in the background — Jibri only becomes HEALTHY (eligible for dispatch) after the probe succeeds
• Retry defaults (6 attempts, 10s delay) accommodate post-reboot delays where Xvfb/Chrome may not be immediately available
• Configurable via jibri.chrome.startup-check, startup-check-max-attempts, and startup-check-retry-delay

Test plan

• Unit tests for EnvironmentChecker (initial UNHEALTHY registration, successful transition, failure persistence, retry-then-succeed)
• Full mvn verify passes (145 tests, 0 failures, ktlint clean)
• Deploy to a test Jibri and verify:
  • Initial XMPP presence shows IDLE + UNHEALTHY
  • After probe succeeds (~seconds), presence updates to IDLE + HEALTHY
  • HTTP /jibri/api/v1.0/health reflects the same transitions
  • Health check script does not trigger shutdown during normal startup window
• Verify startup-check = false preserves old behavior (immediate IDLE + HEALTHY)

[bgrozev]

Suggest to nest the config under a "startup-check" section:
chrome {
startup-check {
enabled = true
max-attempts = 6
retry-delay = 10000
}
}

[aaronkvanmeerten]

Suggest to nest the config under a "startup-check" section:
chrome {
startup-check {
enabled = true
max-attempts = 6
retry-delay = 10000
}
}

Good idea, done.