feat: global AI assistant floating button for supervisors (#578)

- AiFloatingButton: FAB (bottom-right) opens a slide-in drawer with
  the supervisor AI chat panel. Close button collapses drawer, FAB
  reappears. Chat state persists across open/close and page navigation.
- app-shell: mounts FAB for admin users (isAdmin), same pattern as
  CallWidget for agents.
- team-dashboard: removed inline AI panel + toggle button — replaced
  by the global FAB. Dashboard content reclaims the full width.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/shared/ai-floating-button.tsx

@@ -0,0 +1,50 @@
+import { useState } from 'react';
+import { FontAwesomeIcon } from '@fortawesome/react-fontawesome';
+import { faSparkles, faXmark } from '@fortawesome/pro-duotone-svg-icons';
+import { AiChatPanel } from '@/components/call-desk/ai-chat-panel';
+import { cx } from '@/utils/cx';
+
+export const AiFloatingButton = () => {
+    const [open, setOpen] = useState(false);
+
+    return (
+        <>
+            {/* FAB — bottom right, hidden when drawer is open */}
+            {!open && (
+                <button
+                    onClick={() => setOpen(true)}
+                    className="fixed bottom-6 right-6 z-50 flex size-12 items-center justify-center rounded-full bg-brand-solid text-white shadow-lg hover:bg-brand-solid_hover transition duration-100 ease-linear"
+                    title="AI Assistant"
+                >
+                    <FontAwesomeIcon icon={faSparkles} className="size-5" />
+                </button>
+            )}
+
+            {/* Drawer — slides in from right */}
+            <div className={cx(
+                'fixed top-0 right-0 z-50 h-full bg-primary border-l border-secondary shadow-xl transition-all duration-200 ease-linear flex flex-col',
+                open ? 'w-[400px]' : 'w-0 overflow-hidden border-l-0',
+            )}>
+                {open && (
+                    <>
+                        <div className="flex shrink-0 items-center justify-between border-b border-secondary px-4 py-3">
+                            <div className="flex items-center gap-2">
+                                <FontAwesomeIcon icon={faSparkles} className="size-3.5 text-fg-brand-primary" />
+                                <span className="text-sm font-semibold text-primary">AI Assistant</span>
+                            </div>
+                            <button
+                                onClick={() => setOpen(false)}
+                                className="flex size-7 items-center justify-center rounded-lg text-fg-quaternary hover:text-fg-secondary hover:bg-primary_hover transition duration-100 ease-linear"
+                            >
+                                <FontAwesomeIcon icon={faXmark} className="size-4" />
+                            </button>
+                        </div>
+                        <div className="flex-1 min-h-0 overflow-hidden">
+                            <AiChatPanel callerContext={{ type: 'supervisor' }} />
+                        </div>
+                    </>
+                )}
+            </div>
+        </>
+    );
+};