test: adapt suites to the provider-hosted conversation shell

Test-side catch-up with the session-maybe conversation architecture: the
provide channel's descriptor shape and maybeProvideInfo in fakes, the shared
chat-store handle asserted on conversation.session (the session-maybe shell
carries no store), startSession fakes exposing the workspace list snapshot,
strict session slots declining (not throwing) without a session, AppFrame's
removed empty seat and loading gate, and the hero draft asserted on the
machine (the chat-store mirror binds with ConversationSession). Plus three
lint fixes (max-len split, boolean-compare, arrow-parens/unbound-method).

packages/client/ui-layout/tests/apply.spec.ts

@@ -40,7 +40,7 @@ describe('ui-layout client apply', () => {
     expect(slots.entries('root')).toHaveLength(1)
     // …and declared the three children in the ledger.
     expect(slots.spec('sidebar')).toEqual({ kind: 'single', scope: 'root' })
-    expect(slots.spec('conversation')).toEqual({ kind: 'single', scope: 'session' })
+    expect(slots.spec('conversation')).toEqual({ kind: 'single', scope: 'session-maybe' })
     expect(slots.spec('details')).toEqual({ kind: 'single', scope: 'session' })
   })