Detect queued broadcasts that escape capture

[luisdalmolin]

Problem

Queued ShouldBroadcast events handled by an asynchronous queue can leave the in-memory capture scope without producing a capture. The README documents this boundary, but an empty batch can be mistaken for a successful no-op.

Proposed direction

Detect queued BroadcastEvent jobs that escape the capture scope and provide an actionable diagnostic without rejecting synchronous ShouldBroadcastNow events or legitimate broadcastWhen() === false cases.

Acceptance criteria

• An asynchronously queued broadcast produces a targeted diagnostic or inspectable warning.
• Sync queue and ShouldBroadcastNow broadcasts continue to capture normally.
• broadcastWhen() === false is not reported as an escaped queue job.
• Event-specific queue connections and Laravel's default queue connection are covered.
• Documentation explains how to opt into strict capture expectations.