[architecture] Project Memory: serve proposals, drop codemap

_Automatically composed from the parent epic at dispatch time._

7 independent children: serve proposals (+backfill); codemap out of prompt/search + whole-dir batching w/ complete-set retirement; time_bound + path autofill gates; shared used predicate → demotion/read_rate/console sort; strict memory args+aliases; hook lead + command-only followed; settle votes (source settle) + summary followed.