Promote uat → main (PROD): GRO-2373 in-portal chrome sign-out button (web) (#81)

Promote uat → main (PROD): GRO-2373 in-portal chrome sign-out button (web) — cherry-pick of PR #78 (commit 532869f9). UAT_PLAYBOOK §3.2 (TC-WEB-5.25.6f) updated.

Refs: GRO-2360 (P3), GRO-2355 (parent), GRO-2357 (breakdown), GRO-2358 (P1), GRO-2359 (P2).
Co-authored-by: Flea Flicker <22+gb_flea@noreply.git.farh.net>
Co-committed-by: Flea Flicker <22+gb_flea@noreply.git.farh.net>

src/portal/CustomerPortal.tsx

@@ -451,7 +451,14 @@ export function CustomerPortal() {
             })}
           </div>
 
-          {/* Session controls (only shown during active impersonation) */}
+          {/* Session controls — Sign out is always reachable from the portal
+              chrome (GRO-2373). End Impersonation is staff-only and only
+              appears during an active impersonation session. Both share the
+              same LogOut icon for visual consistency, but route to distinct
+              handlers: handleSignOut calls the canonical Better Auth
+              `signOut()` (mirroring OOBE and the no-access card); handleEnd
+              tears down the staff impersonation session and returns to the
+              admin clients list. */}
           <div className="border-t border-stone-100 p-4 space-y-2">
             {session?.status === "active" && (
               <button
@@ -462,6 +469,15 @@ export function CustomerPortal() {
                 End Impersonation
               </button>
             )}
+            <button
+              type="button"
+              onClick={() => { void handleSignOut(); }}
+              className="w-full flex items-center gap-2 px-3 py-2 rounded-lg text-xs font-medium text-stone-700 bg-stone-50 hover:bg-stone-100 transition-colors"
+              data-testid="portal-chrome-signout"
+            >
+              <LogOut size={14} />
+              Sign out
+            </button>
             <div className="flex items-center gap-2 px-3 py-2 text-xs text-stone-400">
               <Shield size={12} />
               Customer Portal v1.0