Phase 4.5: practice area integration in the Next.js UI

Backend commit 26d09d6 introduced a multi-tenant axis (practice_area +
appeal_subtype) that the vanilla UI picked up but the new Next.js
rewrite did not. Close the gap in the screens we already shipped so
future search/filter work in Phase 5 has the right data on screen.

- lib/practice-area.ts — new: enum + label maps + deriveSubtype(),
  mirrors mcp-server/src/legal_mcp/services/practice_area.py.
- lib/schemas/case.ts — two new z.enum fields on caseCreateSchema.
- lib/api/cases.ts — Case / CaseDetail gain practice_area and
  appeal_subtype as optional (cached pre-migration responses still
  parse cleanly).
- wizard/case-wizard.tsx — basics step gains a practice_area dropdown
  (future domains disabled with "(בקרוב)") and an appeal_subtype
  dropdown with auto-fill effect tracking a userTouchedSubtype ref,
  same behaviour as wireSubtypeAutofill() in the vanilla UI.
- cases/case-header.tsx — gold badge next to the status shows
  "ועדת ערר · רישוי ובנייה" when both fields are populated.
- cases/cases-table.tsx — new "תחום" column showing subtype label
  (dash for unknown). No filter yet — that's phase 5 when a second
  domain actually exists.

Plan: ~/.claude/plans/woolly-cooking-graham.md

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

web-ui/src/lib/practice-area.ts

@@ -0,0 +1,72 @@
+/**
+ * Client-side mirror of mcp-server/src/legal_mcp/services/practice_area.py.
+ *
+ * Keep the enum values and derivation logic in sync with the backend — the
+ * server is the authority, but the UI needs the labels and derivation for
+ * UX (auto-fill, badges, filters). If the server adds a new practice_area
+ * or subtype, extend the arrays below.
+ *
+ * See also: legal-ai/docs/practice-area-separation.md
+ */
+
+export type PracticeArea =
+  | "appeals_committee"
+  | "national_insurance"
+  | "labor_law";
+
+export type AppealSubtype =
+  | "building_permit"
+  | "betterment_levy"
+  | "compensation_197"
+  | "unknown";
+
+export const PRACTICE_AREAS: ReadonlyArray<{
+  value: PracticeArea;
+  label: string;
+  enabled: boolean;
+}> = [
+  { value: "appeals_committee",  label: "ועדת ערר",     enabled: true  },
+  { value: "national_insurance", label: "ביטוח לאומי",  enabled: false },
+  { value: "labor_law",          label: "דיני עבודה",   enabled: false },
+];
+
+export const APPEAL_SUBTYPES: ReadonlyArray<{
+  value: AppealSubtype;
+  label: string;
+}> = [
+  { value: "building_permit",  label: "רישוי ובנייה"      },
+  { value: "betterment_levy",  label: "היטל השבחה"        },
+  { value: "compensation_197", label: "פיצויים (ס' 197)"  },
+  { value: "unknown",          label: "לא ידוע"           },
+];
+
+export const PRACTICE_AREA_LABELS: Record<PracticeArea, string> =
+  Object.fromEntries(PRACTICE_AREAS.map((p) => [p.value, p.label])) as Record<
+    PracticeArea,
+    string
+  >;
+
+export const APPEAL_SUBTYPE_LABELS: Record<AppealSubtype, string> =
+  Object.fromEntries(APPEAL_SUBTYPES.map((s) => [s.value, s.label])) as Record<
+    AppealSubtype,
+    string
+  >;
+
+/*
+ * Derive the appeal_subtype from a case number. Mirrors the Python
+ * `derive_subtype` in practice_area.py. The convention is the case-number
+ * first digit: 1xxx → building_permit, 8xxx → betterment_levy,
+ * 9xxx → compensation_197. Everything else, including non-appeals_committee
+ * domains, returns 'unknown'.
+ */
+export function deriveSubtype(
+  caseNumber: string,
+  practiceArea: PracticeArea = "appeals_committee",
+): AppealSubtype {
+  if (practiceArea !== "appeals_committee") return "unknown";
+  const first = caseNumber.trim().match(/^(\d)/)?.[1];
+  if (first === "1") return "building_permit";
+  if (first === "8") return "betterment_levy";
+  if (first === "9") return "compensation_197";
+  return "unknown";
+}