fix(client): contain notification-callback failures and document the source lifecycle

Review follow-ups: the three new notify loops (currentProvideInfo
subscribers, ui-skill lexicon listeners, late-registration controller
setup) now contain per-callback failures so one faulty consumer cannot
starve the rest, abort the list projection pass, or poison the source
roster with no disposer; controller lexicon polling drops a throwing
source with a console record like the candidate path. The ui-slash
README (both languages) now states the late-registration warm and the
subscribeLexicon contract, and the scenario suite drives a typed /name
token gaining its decoration when the roll settles with no further
input.

packages/client/ui-conversation/tests/input-scenarios.spec.tsx

@@ -236,6 +236,35 @@ describe('scenario H: backspace breaks the token', () => {
   })
 })
 
+describe('scenario: reference decoration lights up when the lexicon settles', () => {
+  it('a typed /name token gains the text-ref mark without further input once the roll goes hot', async () => {
+    let roll: readonly string[] | undefined
+    let notify: (() => void) | undefined
+    const b = await scopedBench((slash) => {
+      slash.registerSource({
+        trigger: '/', name: 'skill',
+        candidates: () => Promise.resolve([]),
+        onPick: () => undefined,
+        lexicon: () => roll,
+        subscribeLexicon: (_session: ClientSessionContext, listener: () => void) => {
+          notify = listener
+          return () => { notify = undefined }
+        },
+      } as never)
+    })
+    // Typed before the catalog settled: a plain token, no decoration.
+    b.type('/deploy now')
+    expect(b.view.container.querySelector('[data-decoration="text-ref"]')).toBeNull()
+    // The catalog settles (ui-skill's settle path fires the same notification).
+    act(() => {
+      roll = ['deploy']
+      notify?.()
+    })
+    const mark = b.view.container.querySelector('[data-decoration="text-ref"]')
+    expect(mark?.textContent).toBe('/deploy')
+  })
+})
+
 describe('scenario I: unknown /xyz + enter', () => {
   it('adjudication misses in one hop and the whole line rides the default sink', async () => {
     const b = await bench()