fix(onboarding): shorten the AI pitch on the last setup screen

Every new account finished setup on a full AI panel: a gradient badge, a
sample briefing, three ways to connect a provider, a one-tap offer for the
operator's key and a disclaimer, the most prominent block on the screen.
It is now one muted line with a link to Settings, AI, shown under the same
rule as the Insights hint (could be set up here, nothing configured yet,
not opted out). That hint and the consent request on Insights and
Settings, AI stay the places that invite.

The sample briefing card, the `onboarding.ai.*` strings in ten locales and
the end-to-end spec for the removed offer go with it. The consent-grant
guard's floor drops to the two callers left.

src/__tests__/baselines/source-function-lines.json

@@ -1,7 +1,7 @@
 {
   "$comment": "Production functions over 200 lines, keyed \"file :: name\", and their length. Maintained by src/__tests__/source-size-ratchet.test.ts.",
-  "count": 343,
-  "total": 111236,
+  "count": 342,
+  "total": 110828,
   "entries": {
     "app/achievements/page.tsx :: AchievementsPage": 206,
     "app/api/admin/backups/upload/route.ts :: apiHandler(arg)": 275,
@@ -177,7 +177,6 @@
     "components/mood/mood-list.tsx :: MoodList": 1109,
     "components/mood/mood-tag-picker.tsx :: MoodTagPicker": 257,
     "components/onboarding/confirm-screen.tsx :: ConfirmScreen": 255,
-    "components/onboarding/done-screen.tsx :: DoneScreen": 408,
     "components/onboarding/getting-started-checklist.tsx :: GettingStartedChecklist": 423,
     "components/onboarding/tour.tsx :: OnboardingTour": 544,
     "components/practitioners/practitioner-list.tsx :: PractitionerList": 230,