Own CDP frame applicability and identity at the parsed event boundary. Preserve malformed or incomplete main-frame facts, recognize replacement roots, and carry the same document identity through captures, screenshots, timelines, and execution windows.
Validation: full check:ci and docs:check; 763 browser and dispatch tests passed, 6 skipped. Independent source and fixture-lifecycle review passed. Local real-Chrome behavior was not exercised.
Closes#5665
Sample the browser monotonic clock with observation already subscribed, filter historical lifecycle and network facts, and preserve scope and termination handling when event time is unknown.
Bound pre-arm retention using transport-owned wire bytes. Fail closed when the relevant-event buffer fills, and keep unrelated protocol payloads outside that budget.
BREAKING CHANGE: observe_web_session timeline timestamps can be null when the producer supplies no comparable timestamp. Consumers must handle unknown time explicitly.
Refs #5609
morluto