feat(editor): close the note editor with browser back navigation

The mobile editor is fullscreen with no backdrop to tap, so the Android
back button / iOS back swipe now dismisses it instead of leaving the
page. The editor pushes a shallow-routing history entry on mount and
closes when it is popped; UI closes pop the entry themselves so history
stays clean. NotesView's hash rewriting now goes through SvelteKit's
replaceState so the router keeps handling popstate.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01C1N5Vi12zTez7LNqRvYjUD

src/app.d.ts

@@ -15,7 +15,9 @@ declare global {
 			} | null;
 		}
 		// interface PageData {}
-		// interface PageState {}
+		interface PageState {
+			noteEditorOpen?: boolean;
+		}
 		// interface Platform {}
 	}
 }

src/lib/components/NoteEditor.svelte

@@ -4,6 +4,8 @@
 
 <script lang="ts">
 	import { onMount } from 'svelte';
+	import { pushState } from '$app/navigation';
+	import { page } from '$app/state';
 	import ColorPicker from './ColorPicker.svelte';
 	import Checklist from './Checklist.svelte';
 	import FormattingToolbar from './FormattingToolbar.svelte';
@@ -404,8 +406,34 @@
 		pointerdownOnOverlay = false;
 	}
 
+	// Close on browser back — Android back button / iOS back swipe. The editor is
+	// fullscreen on mobile with no backdrop to tap, so back must dismiss it instead of
+	// leaving the page. On mount, push a shallow-routing history entry; navigating back
+	// pops it and closes the editor. UI closes pop the entry themselves via
+	// history.back() so no stale entry is left behind.
+	let historyEntryPushed = false;
+
+	onMount(() => {
+		// Reuse an existing entry (e.g. back-navigating to a note restored from the
+		// URL hash) instead of stacking a second one.
+		if (!page.state.noteEditorOpen) {
+			pushState('', { noteEditorOpen: true });
+		}
+		historyEntryPushed = true;
+	});
+
+	$effect(() => {
+		if (page.state.noteEditorOpen || !historyEntryPushed || closing) return;
+		historyEntryPushed = false;
+		saveAndClose();
+	});
+
 	function dismissOverlay() {
 		closing = true;
+		if (historyEntryPushed) {
+			historyEntryPushed = false;
+			history.back();
+		}
 		setTimeout(() => onClose(), 400);
 	}
 

src/lib/components/NotesView.svelte

@@ -4,6 +4,7 @@
 	import TagFilter from '$lib/components/TagFilter.svelte';
 	import { pinnedNotes, unpinnedNotes, selectedTag, currentFilter, notes, notesLoaded, loadNotes, updateSortOrders } from '$lib/stores/notes.js';
 	import { onMount } from 'svelte';
+	import { replaceState } from '$app/navigation';
 	import type { Note, NoteFilter } from '$lib/types/index.js';
 	import Plus from 'lucide-svelte/icons/plus';
 	import SquareCheck from 'lucide-svelte/icons/square-check';
@@ -27,16 +28,19 @@
 		loadNotes(filter);
 	});
 
+	// Use SvelteKit's replaceState (not the raw history API) so the router keeps
+	// ownership of the entry — NoteEditor's close-on-back relies on popstate being
+	// handled by SvelteKit.
 	function openEditor(note: Note) {
 		editingNote = note;
-		history.replaceState(null, '', `#${note.id}`);
+		replaceState(`#${note.id}`, {});
 	}
 
 	function closeEditor() {
 		editingNote = null;
 		showNewNote = false;
 		newNoteChecklist = false;
-		history.replaceState(null, '', location.pathname);
+		replaceState(location.pathname, {});
 	}
 
 	function handleReorder(noteIds: string[]) {

tests/e2e/notes-crud.spec.ts

@@ -23,6 +23,40 @@ test.describe('Notes CRUD', () => {
 		await expect(page.getByText('Updated Title')).toBeVisible();
 	});
 
+	test('Scenario: Browser back closes the open editor instead of leaving the page', async ({ authenticatedPage: page }) => {
+		// Given a note titled "Back Closes Me" exists
+		await createNote(page, 'Back Closes Me', 'Some content');
+
+		// Given the note is open in the editor
+		await noteCard(page, 'Back Closes Me').click();
+		await expect(page.getByTestId('note-editor')).toBeVisible();
+
+		// When the user navigates back
+		await page.goBack();
+
+		// Then the editor is closed and the notes list is still shown
+		await expect(page.getByTestId('note-editor')).not.toBeVisible();
+		await expect(noteCard(page, 'Back Closes Me')).toBeVisible();
+	});
+
+	test('Scenario: Closing the editor leaves browser history clean', async ({ authenticatedPage: page }) => {
+		// Given a note titled "Clean History" exists
+		await createNote(page, 'Clean History');
+
+		// Given the user opened and closed the note
+		await noteCard(page, 'Clean History').click();
+		await expect(page.getByTestId('note-editor')).toBeVisible();
+		await page.getByTestId('close-editor-btn').click();
+		await expect(page.getByTestId('note-editor')).not.toBeVisible();
+
+		// When the user navigates back
+		await page.goBack();
+
+		// Then the editor does not reopen and the note's URL is gone from history
+		await expect(page.getByTestId('note-editor')).not.toBeVisible();
+		expect(page.url()).not.toContain('#');
+	});
+
 	test('Scenario: Trashed note disappears from the main view', async ({ authenticatedPage: page }) => {
 		// Given a note titled "Delete Me" exists
 		await createNote(page, 'Delete Me');