Form primitives, keyboard-operable comboboxes, dialog focus, route states

Accessibility work on the UI layer, all of it rooted in one structural gap:
there were no form primitives, so every field was hand-assembled and every
field got the same details wrong.

Form primitives
- components/ui/Field.tsx (Field/TextField/SelectField/TextareaField) and
  Button.tsx. Field generates the control id with useId and derives htmlFor
  from it, which is what makes the association impossible to omit rather
  than merely conventional.
- 92 labels existed, 4 used htmlFor, and no input carried an id at all: a
  screen reader announced an unnamed edit box and clicking a label focused
  nothing. Now every label resolves to its control (0 unassociated), and the
  input class chain that appeared verbatim 85 times appears zero times.
- Field also takes a render prop, so Lookup, CountryPicker and Picklist get
  the same wiring instead of a second, partial solution.
- SearchInput replaces three hand-rolled copies of the icon-in-a-box search
  whose input had only a placeholder — not a label — and killed its own
  focus ring with outline-none and nothing in its place.
- Toggle groups (workdays, reorg change type) became fieldsets with
  aria-pressed; colour alone was carrying the selected state.

Comboboxes
- Lookup and CountryPicker were text inputs with a div of clickable buttons
  underneath: typeable, but no keyboard path to a result and nothing telling
  a screen reader a list had appeared. Both now carry role=combobox,
  aria-expanded/controls/activedescendant and listbox semantics, with arrow
  keys, Enter and Escape. Escape stops propagation, or it would close the
  surrounding dialog along with the dropdown.

Dialogs
- useDialogFocus centralises what Modal and SlideOver each owed the
  keyboard and neither provided beyond Escape: focus into the dialog on
  open, Tab and Shift+Tab cycling within it, focus restored to the trigger
  on close.
- SlideOver stays mounted for its transition, and aria-hidden does not
  remove anything from the tab order — so every closed panel was leaving
  invisible tab stops at the end of the page. `inert` fixes that.

Route states
- loading.tsx, error.tsx, not-found.tsx and global-error.tsx. Every page in
  the (app) group is server-rendered per request, so without loading.tsx a
  navigation showed nothing at all until the server answered, and a render
  error dropped the user on Next's own screen with no way back.

Tests
- 22 component tests (vitest jsdom project). Two of them found limits of the
  environment rather than of the code: jsdom implements neither `inert` nor
  scrollIntoView, so the inert test asserts the attribute and the missing
  scrollIntoView — which was taking the whole render down from inside an
  effect — is stubbed in the setup file.

components/ui/SearchInput.tsx

@@ -0,0 +1,45 @@
+"use client";
+
+import { Search } from "lucide-react";
+import { useId } from "react";
+
+// The icon-in-a-box search field used by the employee list, the audit log and
+// the org chart. Each was a hand-rolled copy whose <input> carried only a
+// placeholder — no label at all — and killed its own focus ring with
+// outline-none. A placeholder is not a label: it disappears on the first
+// keystroke and is not reliably announced.
+export function SearchInput({
+  value,
+  onChange,
+  placeholder,
+  label,
+  className = "",
+}: {
+  value: string;
+  onChange: (value: string) => void;
+  placeholder: string;
+  /** Visually hidden; this is what a screen reader announces. */
+  label: string;
+  className?: string;
+}) {
+  const id = useId();
+  return (
+    <div
+      className={`flex min-w-[240px] flex-1 items-center gap-2 rounded border border-border bg-white px-3 py-2 focus-within:outline-2 focus-within:outline-offset-1 focus-within:outline-brand-500 ${className}`}
+    >
+      <Search className="h-4 w-4 shrink-0 text-ink-muted" aria-hidden />
+      <label htmlFor={id} className="sr-only">
+        {label}
+      </label>
+      <input
+        id={id}
+        type="search"
+        value={value}
+        onChange={(e) => onChange(e.target.value)}
+        placeholder={placeholder}
+        // The ring lives on the wrapper so it encloses the icon too.
+        className="w-full text-sm text-ink outline-none placeholder:text-ink-muted"
+      />
+    </div>
+  );
+}