feat(uat-batch-4): a11y form primitives + click-to-preview + EOI empty-state + lint guards

- FieldError primitive (role=alert, aria-live) — used by Wave 3
  form-error UX work.
- FieldLabel primitive (Label + Info-tooltip slot) — foundational for
  the platform-wide admin-settings tooltip audit.
- ESLint guard against em-dash in user-facing JSX text inside
  src/components + src/app (warning, not error; 111 existing instances
  flagged for follow-up sweep).
- FileGrid card body becomes click-to-preview button (was hidden under
  a kebab); aria-label per row; kebab keeps Download/Rename/Delete.
- DocumentList: title cell on rows with signedFileId opens
  FilePreviewDialog; kebab gains Download action (was missing
  per UAT). Single FilePreviewDialog instance lifted to the parent.
- DocumentList type extended with signedFileId.
- EOI empty state: third ghost button "Mark signed without file"
  wired to existing MarkExternallySignedDialog (parity with
  reservation tab).
- Watcher empty-state padding fix on document-detail.

tsc clean. 1419/1419 vitest. lint clean on touched files.

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

src/components/ui/field-error.tsx

@@ -0,0 +1,48 @@
+'use client';
+
+import * as React from 'react';
+
+import { cn } from '@/lib/utils';
+
+export interface FieldErrorProps extends React.HTMLAttributes<HTMLParagraphElement> {
+  /**
+   * The error message to render. When falsy the component renders an
+   * empty live region so a screen reader still picks up subsequent
+   * error messages without an aria-live remount.
+   */
+  message?: string | null | undefined;
+  /**
+   * Optional id — pair with `aria-describedby` on the associated input
+   * so SR users hear the error after the input's accessible name.
+   */
+  id?: string;
+}
+
+/**
+ * Accessible error renderer for form fields. Always renders a
+ * `role="alert"` + `aria-live="polite"` region so SR users get
+ * immediate feedback when validation fires. Hide visually when
+ * `message` is empty without removing the region from the DOM —
+ * tearing the live region down between submits delays the next
+ * announcement on most assistive tech.
+ *
+ * Caller is responsible for setting `aria-invalid` and
+ * `aria-describedby={id}` on the linked input.
+ */
+export function FieldError({ message, id, className, ...props }: FieldErrorProps) {
+  return (
+    <p
+      id={id}
+      role="alert"
+      aria-live="polite"
+      className={cn(
+        'text-xs text-destructive',
+        !message && 'sr-only', // empty state keeps the region for next message
+        className,
+      )}
+      {...props}
+    >
+      {message ?? ''}
+    </p>
+  );
+}

src/components/ui/field-label.tsx

@@ -0,0 +1,66 @@
+'use client';
+
+import * as React from 'react';
+import { Info } from 'lucide-react';
+
+import { Label } from '@/components/ui/label';
+import { Tooltip, TooltipContent, TooltipProvider, TooltipTrigger } from '@/components/ui/tooltip';
+import { cn } from '@/lib/utils';
+
+export interface FieldLabelProps extends React.ComponentPropsWithoutRef<typeof Label> {
+  /**
+   * Optional explainer copy. When set, an Info icon is rendered next
+   * to the label that opens a Tooltip on hover / focus. Tooltip writing
+   * guidelines: 1-2 sentences max; state the unit ("...in days",
+   * "...in MB"); lead with the risk for dangerous settings; explain the
+   * "why and how to choose a value" rather than restating the label.
+   */
+  tooltip?: React.ReactNode;
+  /** Mark the field as required — appends an asterisk after the label text. */
+  required?: boolean;
+}
+
+/**
+ * Shared label-with-explainer primitive for admin forms. Wraps the
+ * shadcn Label + an optional Info-tooltip slot. Adopting this everywhere
+ * an admin setting needs a non-obvious explainer (Sort Order, Weight,
+ * TTL, Cap, Confidence, Threshold) gives admins consistent tooltip UX
+ * without per-form bespoke implementations.
+ */
+export function FieldLabel({
+  tooltip,
+  required,
+  className,
+  children,
+  ...labelProps
+}: FieldLabelProps) {
+  if (!tooltip) {
+    return (
+      <Label className={cn('inline-flex items-center gap-1.5', className)} {...labelProps}>
+        {children}
+        {required ? <span aria-hidden>*</span> : null}
+      </Label>
+    );
+  }
+
+  return (
+    <Label className={cn('inline-flex items-center gap-1.5', className)} {...labelProps}>
+      {children}
+      {required ? <span aria-hidden>*</span> : null}
+      <TooltipProvider delayDuration={200}>
+        <Tooltip>
+          <TooltipTrigger asChild>
+            <button
+              type="button"
+              aria-label="More info"
+              className="text-muted-foreground hover:text-foreground focus:outline-none focus:ring-2 focus:ring-ring focus:ring-offset-2 rounded-sm"
+            >
+              <Info className="h-3.5 w-3.5" aria-hidden />
+            </button>
+          </TooltipTrigger>
+          <TooltipContent className="max-w-xs text-xs leading-relaxed">{tooltip}</TooltipContent>
+        </Tooltip>
+      </TooltipProvider>
+    </Label>
+  );
+}