Transcript now shows a spacer marking where context was cleared

The interactive session UI now instantiates a dedicated store (class qie) that records where a view-clear happened, tracking clearedAfter/conversationKey against the transcript and firing telemetry when it's invoked. It's threaded into the main session component as a new clearedView prop and disposed alongside the other session-lifecycle objects.

The message-list renderer threads this clearedAfter value through props and computes a render index (j5e = JJo.count(xv, NE, FJo) - 1) at which it inserts a spacer element keyed cleared-${id} with a blank height equal to the viewport rows, similar to the existing 'unseen messages' divider. This gives a visual break in the transcript at the point context was cleared (e.g. via /clear or compaction), rather than showing cleared and post-clear messages contiguously.