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/error.test.ts

@@ -0,0 +1,114 @@
+import "@testing-library/jest-dom/vitest";
+import { afterEach, describe, expect, it, vi } from "vitest";
+import { ConnectError, Code } from "@connectrpc/connect";
+
+import { AuthError } from "../src/api/auth";
+import {
+	classifyError,
+	isRetryable,
+	type ErrorKind,
+} from "../src/lib/error/classify";
+import { errorMessageKey, reportError } from "../src/lib/error/report";
+import { toast } from "../src/lib/toast.svelte";
+
+afterEach(() => {
+	toast.resetForTests();
+	vi.restoreAllMocks();
+});
+
+describe("classifyError", () => {
+	it("maps HTTP statuses (AuthError) to kinds", () => {
+		const at = (status: number) =>
+			classifyError(new AuthError("x", "msg", status));
+		expect(at(401)).toBe("auth");
+		expect(at(403)).toBe("forbidden");
+		expect(at(404)).toBe("notFound");
+		expect(at(409)).toBe("conflict");
+		expect(at(429)).toBe("rateLimit");
+		expect(at(500)).toBe("server");
+		expect(at(400)).toBe("unknown");
+	});
+
+	it("maps Connect codes to kinds", () => {
+		const at = (code: Code) => classifyError(new ConnectError("msg", code));
+		expect(at(Code.Unauthenticated)).toBe("auth");
+		expect(at(Code.PermissionDenied)).toBe("forbidden");
+		expect(at(Code.NotFound)).toBe("notFound");
+		expect(at(Code.FailedPrecondition)).toBe("conflict");
+		expect(at(Code.ResourceExhausted)).toBe("rateLimit");
+		expect(at(Code.Unavailable)).toBe("network");
+		expect(at(Code.Internal)).toBe("server");
+	});
+
+	it("treats a fetch TypeError as a network error", () => {
+		expect(classifyError(new TypeError("Failed to fetch"))).toBe("network");
+	});
+
+	it("duck-types any object with a numeric status", () => {
+		expect(classifyError({ status: 409 })).toBe("conflict");
+	});
+
+	it("falls back to unknown for a plain error", () => {
+		expect(classifyError(new Error("boom"))).toBe("unknown");
+	});
+
+	it("short-circuits to offline when the browser is offline", () => {
+		Object.defineProperty(navigator, "onLine", {
+			configurable: true,
+			value: false,
+		});
+		try {
+			expect(classifyError(new AuthError("x", "m", 500))).toBe("offline");
+		} finally {
+			Object.defineProperty(navigator, "onLine", {
+				configurable: true,
+				value: true,
+			});
+		}
+	});
+
+	it("marks only transient kinds retryable", () => {
+		const retryable: ErrorKind[] = ["offline", "network", "server"];
+		const notRetryable: ErrorKind[] = [
+			"auth",
+			"forbidden",
+			"conflict",
+			"notFound",
+			"rateLimit",
+			"unknown",
+		];
+		expect(retryable.every(isRetryable)).toBe(true);
+		expect(notRetryable.some(isRetryable)).toBe(false);
+	});
+});
+
+describe("reportError / errorMessageKey", () => {
+	it("returns the translated message key for inline use", () => {
+		expect(errorMessageKey(new AuthError("x", "m", 403))).toBe("error.forbidden");
+		expect(errorMessageKey(new Error("?"))).toBe("error.unknown");
+	});
+
+	it("raises an auto-dismiss toast for a non-retryable error", () => {
+		const kind = reportError(new AuthError("x", "m", 403));
+		expect(kind).toBe("forbidden");
+		expect(toast.current?.messageKey).toBe("error.forbidden");
+		expect(toast.current?.actionLabelKey).toBeUndefined();
+		expect(toast.current?.durationMs).toBe(8000);
+	});
+
+	it("raises a sticky Retry toast for a retryable error with onRetry", () => {
+		const onRetry = vi.fn();
+		const kind = reportError(new TypeError("Failed to fetch"), { onRetry });
+		expect(kind).toBe("network");
+		expect(toast.current?.messageKey).toBe("error.network");
+		expect(toast.current?.actionLabelKey).toBe("common.retry");
+		expect(toast.current?.durationMs).toBeNull();
+		toast.current?.onAction?.();
+		expect(onRetry).toHaveBeenCalledOnce();
+	});
+
+	it("does not add a Retry action to a non-retryable error", () => {
+		reportError(new AuthError("x", "m", 403), { onRetry: vi.fn() });
+		expect(toast.current?.actionLabelKey).toBeUndefined();
+	});
+});