Session-projection capability family: the seam through which domain host plugins serve whole current values of log-derived per-session state to client carriers.

Package	ctx key	Role
`session-projection`	`sessionProjections`	The interface package: the merge-extensible `SessionProjectionMap` type table, the `ProjectionDefinition` unit contract, and the eagerly driven registry carriers read synchronously
`session-projection-cache`	`sessionProjectionCache`	Persisted projection cache: durable per-session unit checkpoints over the domain data form, throttled write-behind with mandatory turn/end + detach points, and the cold-read ladder (cache row + persistence tail replay)