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/src/lib/active-view/mail/compose.svelte

@@ -11,6 +11,7 @@ surfaces the resulting 403 inline.
 
 	import { i18n } from "$lib/i18n/index.svelte";
 	import { trapFocus } from "$lib/a11y/focus-trap";
+	import { errorMessageKey } from "$lib/error";
 	import { mailStore } from "$lib/mail-store.svelte";
 	import {
 		RENDERED_REPORT_CONTEXT_KEY,
@@ -82,7 +83,7 @@ surfaces the resulting 403 inline.
 			await mailStore.composeBroadcast({ subject, body: bodyText });
 			onSent(null);
 		} catch (err) {
-			error = err instanceof Error ? err.message : String(err);
+			error = i18n.t(errorMessageKey(err));
 		} finally {
 			sending = false;
 		}