After each navigation, probe the loaded page for known behavioural anti-bot
vendor fingerprints — cookies (_abck/Akamai, _px/PerimeterX, datadome,
reese84/Imperva, …), script URLs, and window globals — and escalate this
session to HumanizeLevel::Human when one is present, else fall back to the Off
baseline. So ordinary sites run at full speed (instant clicks) and only pages
actually guarded by behavioural detection pay for human-like motion.
`AGENT_BROWSER_HUMANIZE` still forces a fixed level and short-circuits the probe.
Best-effort: a failed probe leaves the level unchanged. Verified end-to-end
(headless --launch): a HUMANIZE=human click on example.com traverses the curved
trajectory and lands correctly (→ iana.org), identical outcome to Off.