Discussionary Digest Throughline Workflow

Once a digest is active, continue it by default when the user says same digest, gives strategic thoughts in the same discussion thread, asks for a response in the doc, or otherwise continues the active topic.

If the active discussion produces candidate signals, also update RESEARCH/EGG_FUND/signals/signal-catalog.md.

This throughline workflow does not authorize deck drafting, final application copy, polished narrative, final offering composition, or artifact packaging. Those phases still begin only when MJF explicitly signals that they have begun.