feat(uat-batch): Groups J + K — activity feed + onboarding resolver-chain

J38, J39, K40 (core) from the 2026-05-21 plan.

Shipped:
  J38  EntityActivityFeed sentence rendering surfaces the new value
       inline. Was "<actor> updated the X"; now "<actor> set X to
       <value>" when the audit row carries `newValue`. Field-level
       diff line underneath keeps showing the old → new strikethrough
       for context. Truncates inline value at 60 chars to keep long
       notes / descriptions from blowing out the row.
  J39  Client → Companies tab CTA. Empty state gains a "Link to a
       company" action; populated state grows a top-right "Link to
       company" button. New <LinkCompanyDialog> wraps the existing
       <CompanyPicker> + a membership-role select + an "is primary"
       checkbox, then POSTs to /api/v1/companies/[id]/members.
       Empty-state copy dropped "Add a membership from a company's
       detail page" — the rep can act inline now.
  K40  OnboardingChecklist resolver-chain. The auto-check no longer
       reads raw `/admin/settings` rows (which miss env fallbacks).
       Resolved endpoint widened to accept `?keys=k1,k2,...` so the
       checklist can batch-resolve any heterogenous set of registry
       keys through port → global → env → default in one round-trip.
       Checklist captures the dominant source per step ("env fallback",
       "global default", "built-in default") and surfaces it inline
       under the green tick so super-admins see when a step is
       relying on env rather than a per-port override. Compound-key
       gates report the weakest sub-key's source so a partially-env
       config still flags clearly.
       Topbar banner / dashboard tile / weekly nudge / celebration
       sub-items remain queued — the core resolver-chain gap was
       the actual cause of the "step never ticks" UAT complaint.

Verified: tsc clean, vitest 1454/1454.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/clients/client-companies-tab.tsx

@@ -1,8 +1,12 @@
 'use client';
 
+import { useState } from 'react';
 import Link from 'next/link';
 import { useParams } from 'next/navigation';
 import { format } from 'date-fns';
+import { useMutation, useQueryClient } from '@tanstack/react-query';
+import { Building2, Plus } from 'lucide-react';
+import { toast } from 'sonner';
 
 import {
   Table,
@@ -13,7 +17,27 @@ import {
   TableRow,
 } from '@/components/ui/table';
 import { Badge } from '@/components/ui/badge';
+import { Button } from '@/components/ui/button';
 import { EmptyState } from '@/components/shared/empty-state';
+import {
+  Dialog,
+  DialogContent,
+  DialogDescription,
+  DialogFooter,
+  DialogHeader,
+  DialogTitle,
+} from '@/components/ui/dialog';
+import { Label } from '@/components/ui/label';
+import {
+  Select,
+  SelectContent,
+  SelectItem,
+  SelectTrigger,
+  SelectValue,
+} from '@/components/ui/select';
+import { CompanyPicker } from '@/components/companies/company-picker';
+import { apiFetch } from '@/lib/api/client';
+import { toastError } from '@/lib/api/toast-error';
 
 interface ClientCompaniesTabProps {
   clientId: string;
@@ -37,22 +61,45 @@ function formatSince(startDate: string | Date): string {
   return format(d, 'MMM d, yyyy');
 }
 
-export function ClientCompaniesTab({ clientId: _clientId, companies }: ClientCompaniesTabProps) {
+export function ClientCompaniesTab({ clientId, companies }: ClientCompaniesTabProps) {
   const routeParams = useParams<{ portSlug: string }>();
   const portSlug = routeParams?.portSlug ?? '';
+  const [linkOpen, setLinkOpen] = useState(false);
 
   if (companies.length === 0) {
     return (
-      <EmptyState
-        title="No company memberships"
-        description="This client is not affiliated with any companies yet. Add a membership from a company's detail page."
-      />
+      <>
+        <EmptyState
+          title="No company memberships"
+          description="This client is not affiliated with any companies yet."
+          icon={Building2}
+          action={{ label: 'Link to a company', onClick: () => setLinkOpen(true) }}
+        />
+        <LinkCompanyDialog
+          open={linkOpen}
+          onOpenChange={setLinkOpen}
+          clientId={clientId}
+          portSlug={portSlug}
+        />
+      </>
     );
   }
 
   return (
     <div className="space-y-4">
-      <h3 className="text-sm font-medium">Company affiliations</h3>
+      <div className="flex items-center justify-between">
+        <h3 className="text-sm font-medium">Company affiliations</h3>
+        <Button size="sm" variant="outline" onClick={() => setLinkOpen(true)}>
+          <Plus className="mr-1.5 h-3.5 w-3.5" aria-hidden />
+          Link to company
+        </Button>
+      </div>
+      <LinkCompanyDialog
+        open={linkOpen}
+        onOpenChange={setLinkOpen}
+        clientId={clientId}
+        portSlug={portSlug}
+      />
       <div className="rounded-md border">
         <Table>
           <TableHeader>
@@ -101,3 +148,104 @@ export function ClientCompaniesTab({ clientId: _clientId, companies }: ClientCom
     </div>
   );
 }
+
+interface LinkCompanyDialogProps {
+  open: boolean;
+  onOpenChange: (next: boolean) => void;
+  clientId: string;
+  portSlug: string;
+}
+
+const MEMBERSHIP_ROLES = [
+  { value: 'director', label: 'Director' },
+  { value: 'shareholder', label: 'Shareholder' },
+  { value: 'employee', label: 'Employee' },
+  { value: 'agent', label: 'Agent' },
+  { value: 'beneficial_owner', label: 'Beneficial owner' },
+  { value: 'authorised_signatory', label: 'Authorised signatory' },
+  { value: 'other', label: 'Other' },
+];
+
+function LinkCompanyDialog({ open, onOpenChange, clientId, portSlug }: LinkCompanyDialogProps) {
+  const [companyId, setCompanyId] = useState<string | null>(null);
+  const [role, setRole] = useState<string>('director');
+  const [isPrimary, setIsPrimary] = useState(false);
+  const qc = useQueryClient();
+
+  const create = useMutation({
+    mutationFn: async () => {
+      if (!companyId) throw new Error('Pick a company');
+      await apiFetch(`/api/v1/companies/${companyId}/members`, {
+        method: 'POST',
+        body: { clientId, role, isPrimary },
+      });
+    },
+    onSuccess: () => {
+      toast.success('Membership added');
+      void qc.invalidateQueries({ queryKey: ['clients', clientId] });
+      setCompanyId(null);
+      setRole('director');
+      setIsPrimary(false);
+      onOpenChange(false);
+    },
+    onError: (err) => toastError(err),
+  });
+
+  return (
+    <Dialog open={open} onOpenChange={onOpenChange}>
+      <DialogContent>
+        <DialogHeader>
+          <DialogTitle>Link client to a company</DialogTitle>
+          <DialogDescription>
+            Pick an existing company or{' '}
+            <Link
+              /* eslint-disable-next-line @typescript-eslint/no-explicit-any */
+              href={`/${portSlug}/companies?create=1` as any}
+              className="text-primary hover:underline"
+            >
+              create a new one
+            </Link>
+            , then choose this client&apos;s role in it.
+          </DialogDescription>
+        </DialogHeader>
+        <div className="space-y-3 py-2">
+          <div className="space-y-1">
+            <Label>Company</Label>
+            <CompanyPicker value={companyId} onChange={setCompanyId} />
+          </div>
+          <div className="space-y-1">
+            <Label>Role</Label>
+            <Select value={role} onValueChange={setRole}>
+              <SelectTrigger>
+                <SelectValue />
+              </SelectTrigger>
+              <SelectContent>
+                {MEMBERSHIP_ROLES.map((r) => (
+                  <SelectItem key={r.value} value={r.value}>
+                    {r.label}
+                  </SelectItem>
+                ))}
+              </SelectContent>
+            </Select>
+          </div>
+          <label className="flex items-center gap-2 text-sm">
+            <input
+              type="checkbox"
+              checked={isPrimary}
+              onChange={(e) => setIsPrimary(e.target.checked)}
+            />
+            Set as primary affiliation
+          </label>
+        </div>
+        <DialogFooter>
+          <Button variant="outline" onClick={() => onOpenChange(false)}>
+            Cancel
+          </Button>
+          <Button onClick={() => create.mutate()} disabled={create.isPending || !companyId}>
+            Link
+          </Button>
+        </DialogFooter>
+      </DialogContent>
+    </Dialog>
+  );
+}