feat(ui): error & state UX — error surface, view states, map selection, sheet gestures (F4)

- lib/error/: classify any caught error into a stable ErrorKind from the
  transport signal (HTTP status / Connect Code / fetch TypeError /
  navigator.onLine); map to translated error.* messages via reportError
  (sticky Retry toast for retryable kinds) or errorMessageKey (inline).
  Mail compose now surfaces the translated 403/error inline.
- lib/ui/view-state.svelte: shared loading/empty/error placeholder with
  the right live-region role + optional action; entity tables
  (races/sciences/ship-classes) migrated, rest adopt incrementally.
- map/selection-ring.ts: accent ring around the selected planet, fed into
  the map buildExtras alongside the reach circles.
- lib/ui/sheet-dismiss.ts: tap-outside + drag-handle swipe-down dismissal
  for the planet/ship-group bottom-sheets (hand-rolled pointer events).

Tests: error, view-state, selection-ring, sheet-dismiss (761 total).
Docs: ui/docs/error-state-ux.md (+ index); F4 marked done.

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

ui/frontend/tests/view-state.test.ts

@@ -0,0 +1,45 @@
+import "@testing-library/jest-dom/vitest";
+import { fireEvent, render } from "@testing-library/svelte";
+import { describe, expect, it, vi } from "vitest";
+
+import ViewState from "../src/lib/ui/view-state.svelte";
+
+describe("ViewState", () => {
+	it("announces an error assertively (role=alert)", () => {
+		const ui = render(ViewState, {
+			props: { kind: "error", message: "it broke", testid: "vs" },
+		});
+		const el = ui.getByTestId("vs");
+		expect(el).toHaveAttribute("role", "alert");
+		expect(el).toHaveAttribute("data-kind", "error");
+		expect(el).toHaveTextContent("it broke");
+	});
+
+	it("announces loading politely (role=status)", () => {
+		const ui = render(ViewState, {
+			props: { kind: "loading", message: "loading…" },
+		});
+		expect(ui.getByRole("status")).toHaveTextContent("loading…");
+	});
+
+	it("renders an action button that fires onAction", async () => {
+		const onAction = vi.fn();
+		const ui = render(ViewState, {
+			props: {
+				kind: "error",
+				message: "failed",
+				actionLabel: "retry",
+				onAction,
+			},
+		});
+		await fireEvent.click(ui.getByText("retry"));
+		expect(onAction).toHaveBeenCalledOnce();
+	});
+
+	it("omits the action button when no handler is given", () => {
+		const ui = render(ViewState, {
+			props: { kind: "empty", message: "nothing here" },
+		});
+		expect(ui.queryByRole("button")).toBeNull();
+	});
+});