On a shared kanban.db, every home's profile_exists('default') is
unconditionally True, so any home's dispatcher could claim cards assigned
to 'default'. Wrap the _profile_exists_fn() predicate with an optional
per-home allowlist: kanban.dispatch_profiles (config.yaml, list or
comma-separated string) with a HERMES_KANBAN_DISPATCH_PROFILES env bridge.
Unset preserves upstream behavior; 'none' claims nothing. Foreign
assignees land in the existing skipped_nonspawnable bucket, and the gate
applies to the ready spawn path, _has_spawnable, and review dispatch alike.
Also documents the multi-home default collision in the kanban user guide.
Fixes#110995
Kevin Rajan
2d46af3fa2