feat(transcribe): wire keyboard shortcuts into the document panel (#327)

Attaches the transcribeShortcuts action to the document page and wires every
command to existing context setters: j/k walk the sortOrder-sorted regions
and set activeAnnotationId, e toggles read/edit, n arms a draw cue (edit
only), Delete routes to the existing confirm path, ? opens the cheatsheet,
and Esc is now owned solely by the action — the inline onMount Esc listener
is removed (decision B1). Renders ShortcutCheatsheet and a draw-armed hint.

"t" toggles the document-level KURRENT_RECOGNITION training enrollment (the
only training surface that exists; there is no per-region flag yet — see
#321) and no-ops unless a region is active. Also reconciles annotation
Delete: the shape no longer self-handles the key, with onfocus syncing the
active region so the action deletes exactly once.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/document/annotation/AnnotationShape.svelte

@@ -1,5 +1,6 @@
 <script lang="ts">
 import type { Annotation } from '$lib/shared/types';
+import { m } from '$lib/paraglide/messages.js';
 import AnnotationEditOverlay from './AnnotationEditOverlay.svelte';
 
 let {
@@ -12,8 +13,8 @@ let {
 	isFlashing = false,
 	isResizable = false,
 	showDelete = false,
-	onDeleteRequest,
 	onclick,
+	onfocus,
 	onpointerenter,
 	onpointerleave
 }: {
@@ -26,12 +27,17 @@ let {
 	isFlashing?: boolean;
 	isResizable?: boolean;
 	showDelete?: boolean;
-	onDeleteRequest?: () => void;
 	onclick: () => void;
+	onfocus?: () => void;
 	onpointerenter: () => void;
 	onpointerleave: () => void;
 } = $props();
 
+// When deletion is available (transcribe mode), announce the otherwise-hidden
+// Delete affordance to assistive tech (issue #327). The transcribeShortcuts
+// action is the single owner of the key itself.
+const ariaLabel = $derived(showDelete ? m.annotation_label_with_delete() : 'Block anzeigen');
+
 function hexToRgba(hex: string, alpha: number): string {
 	const r = parseInt(hex.slice(1, 3), 16);
 	const g = parseInt(hex.slice(3, 5), 16);
@@ -83,11 +89,12 @@ let shapeStyle = $derived(
 	class:annotation-flash={isFlashing}
 	role="button"
 	tabindex="0"
-	aria-label="Block anzeigen"
+	aria-label={ariaLabel}
+	aria-keyshortcuts={showDelete ? 'Delete' : undefined}
 	onclick={onclick}
+	onfocus={onfocus}
 	onkeydown={(e) => {
 		if (e.key === 'Enter' || e.key === ' ') onclick();
-		if (e.key === 'Delete' && showDelete) onDeleteRequest?.();
 	}}
 	onpointerenter={onpointerenter}
 	onpointerleave={onpointerleave}