feat: add inline-editable summary field to group header

Click the group name in edit mode to rename it inline. The input
replaces the label, saves on blur/Enter, and cancels on Escape.
Wired from both GroupOverlay and CollapsedGroupNode.

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

frontend/src/lib/components/graph/GroupNodeCard.svelte

@@ -3,6 +3,7 @@
 	import { getNodeColorClasses } from '$lib/components/graph'
 	import { NOTE_COLORS, NoteColor } from './noteColors'
 	import { twMerge } from 'tailwind-merge'
+	import { preventDefault, stopPropagation } from 'svelte/legacy'
 	import GroupNoteArea from './GroupNoteArea.svelte'
 
 	interface Props {
@@ -14,6 +15,7 @@
 		note?: string
 		showNote?: boolean
 		editMode?: boolean
+		onSummaryUpdate?: (text: string) => void
 		onNoteUpdate?: (text: string) => void
 		onHeightChange?: (height: number) => void
 	}
@@ -27,6 +29,7 @@
 		note,
 		showNote = false,
 		editMode = false,
+		onSummaryUpdate,
 		onNoteUpdate,
 		onHeightChange
 	}: Props = $props()
@@ -37,6 +40,37 @@
 
 	let defaultColorClasses = $derived(getNodeColorClasses(undefined, selected))
 
+	// Inline summary editing
+	let editingSummary = $state(false)
+	let summaryInput = $state('')
+	let summaryInputElement: HTMLInputElement | undefined = $state(undefined)
+
+	function startEditingSummary() {
+		if (!editMode) return
+		editingSummary = true
+		summaryInput = summary ?? ''
+		requestAnimationFrame(() => {
+			summaryInputElement?.focus()
+			summaryInputElement?.select()
+		})
+	}
+
+	function saveSummary() {
+		editingSummary = false
+		const trimmed = summaryInput.trim()
+		if (trimmed !== (summary ?? '')) {
+			onSummaryUpdate?.(trimmed)
+		}
+	}
+
+	function handleSummaryKeydown(event: KeyboardEvent) {
+		if (event.key === 'Enter') {
+			saveSummary()
+		} else if (event.key === 'Escape') {
+			editingSummary = false
+		}
+	}
+
 	// Reset height to 0 when note is hidden
 	$effect(() => {
 		if (!showNote) {
@@ -63,7 +97,27 @@
 	></div>
 	<div class="flex items-center w-full gap-1.5 px-2 h-[34px] relative z-1">
 		<Group size={14} />
-		<span class="text-2xs font-medium truncate">{summary || 'Group'}</span>
+		{#if editingSummary}
+			<input
+				bind:this={summaryInputElement}
+				bind:value={summaryInput}
+				class="text-2xs font-medium bg-transparent border-none p-0 m-0 outline-none min-w-0 flex-1 nodrag nowheel"
+				placeholder="Group"
+				onblur={saveSummary}
+				onkeydown={handleSummaryKeydown}
+				onclick={stopPropagation(preventDefault(() => {}))}
+				onpointerdown={stopPropagation(() => {})}
+				spellcheck="false"
+			/>
+		{:else}
+			<!-- svelte-ignore a11y_click_events_have_key_events -->
+			<!-- svelte-ignore a11y_no_static_element_interactions -->
+			<span
+				class="text-2xs font-medium truncate {editMode ? 'cursor-text hover:opacity-80' : ''}"
+				onclick={editMode ? stopPropagation(preventDefault(startEditingSummary)) : undefined}
+				onpointerdown={editMode ? stopPropagation(preventDefault(() => {})) : undefined}
+			>{summary || 'Group'}</span>
+		{/if}
 		{#if stepCount != null}
 			<span class="text-2xs opacity-60">{stepCount} node{stepCount !== 1 ? 's' : ''}</span>
 		{/if}

frontend/src/lib/components/graph/GroupOverlay.svelte

@@ -148,6 +148,7 @@
 							note={group.note}
 							showNote={showNotes && group.note != null}
 							{editMode}
+							onSummaryUpdate={(text) => groupEditorContext?.groupEditor.updateSummary(group.id, text)}
 							onNoteUpdate={(text) => groupEditorContext?.groupEditor.updateNote(group.id, text)}
 							onHeightChange={(h) => groupEditorContext?.groupEditor.setNoteHeight(group.id, h)}
 						/>

frontend/src/lib/components/graph/renderers/nodes/CollapsedGroupNode.svelte

@@ -38,6 +38,8 @@
 				note={data.note}
 				showNote={data.showNotes && data.note != null}
 				editMode={data.editMode}
+				onSummaryUpdate={(text) =>
+					groupEditorContext?.groupEditor.updateSummary(data.groupId, text)}
 				onNoteUpdate={(text) =>
 					groupEditorContext?.groupEditor.updateNote(data.groupId, text)}
 				onHeightChange={(h) =>