feat(ui-slots): bind inject hooks compartments into use<Name> selector hooks

Registrant-private reactive facts previously reached components as raw
observables that each component subscribed by hand (InputBar notices/
lexicon via uSES, SettingsRoot via a version/subscribe/getter triple).
The inject face now carries a reserved hooks compartment of bare
sources; the renderer binds each into a use<Name> selector hook through
the same machinery as the provide channel, so components consume
useNotices/useLexicon/useSections and never see a subscription
primitive. InputBar and SettingsRoot are the first two consumers.

packages/client/ui-conversation/tests/skeleton.spec.tsx

@@ -118,6 +118,8 @@ function mount(
           useInput={useInput}
           inputActions={inputActions}
           keyboard={wiring}
+          useNotices={bindSnapshotSelector(wiring.notices)}
+          useLexicon={bindSnapshotSelector(wiring.lexicon)}
           stop={stop}
           renderSlot={(() => null) as InputBarProps['renderSlot']}
           {...bar}