CngxMatTabsRegistry

Sibling host-directive that owns the per-MatTab handle registry for [cngxMatTabs]. Keeps the parent under the level-4 organism LOC guard and lets per-tab decoration directives reach the registry through a typed token.

Owns: contentChildren(MatTab) query, the order-aware registration seam (per-tab cngx setup paired with a child EnvironmentInjector scoping the _stateChanges bridge), an effect() that mirrors the MatTab query order into CNGX_TAB_GROUP_HOST on every emission, and a DestroyRef cleanup that unregisters and destroys every entry.

Order matters: the presenter registry appends new registrations, but Material renders tabs at their DOM position - a mid-list <mat-tab> insert must land at its query index, not at the tail, or index-based selection, announcements and decorations target the wrong tab. The shared seam re-registers the diverging suffix in query order while keeping surviving handle instances (and their child injectors) alive.

Composition: [cngxMatTabs] declares this in hostDirectives; both share the parent's CngxTabGroupPresenter and the same <mat-tab-group> content-children scope.