feat: closing the tab warns about a document that has no file

The unload warning followed the changes a file had not got yet; a document
that never was a file got none, on the grounds that the autosave keeps it.
It now warns as soon as such a document has content — the same emptiness
test the confirm before a new document uses.

src/App.svelte

@@ -166,8 +166,8 @@
   let dirty = $state(false);
   let cleanSum: number | null = null;
   let sumTimer: ReturnType<typeof setTimeout> | undefined;
-  // Whether there is a file to lose those changes from. A document that only ever
-  // lived in the browser is kept by the autosave, so leaving is not worth a warning.
+  // Whether there is a file to lose those changes from — a saved file makes the dot,
+  // and the unload warning, follow the changes rather than the document's existence.
   let documentHasFile = $state(false);
 
   // The page count rides in with the zones but is a layout result, not an edit: a
@@ -202,7 +202,10 @@
   });
 
   $effect(() => {
-    if (!dirty || !documentHasFile) return;
+    // A document with no file behind it lives in this browser alone, so closing the tab
+    // is worth the browser's warning as much as changes a file has not got yet. The
+    // same emptiness test the confirm before a new document uses.
+    if (documentHasFile ? !dirty : tick < 0 || !isDocNonEmpty()) return;
     const warn = (e: BeforeUnloadEvent) => e.preventDefault();
     addEventListener('beforeunload', warn);
     return () => removeEventListener('beforeunload', warn);

src/lib/components/CLAUDE.md

@@ -228,8 +228,9 @@ settle pass or the spell checker keeps the document moving), and the baseline is
 **synchronously** on the effect's first run, not in that timer: under a repagination the
 timer can be pushed out past the reader's first edit, which would make that edit the
 baseline. A save, an open or a new document takes a fresh baseline (`markSaved`).
-Leaving the page warns only when the document actually has a file — a browser-only document
-is kept by the autosave, so there would be nothing to lose.
+Leaving the page warns while a document with a file differs from it, and for a document
+with no file at all as soon as it has content (the emptiness test the confirm before a new
+document uses). The wording is the browser's own — `beforeunload` carries no message.
 
 ## Built-in templates (`TemplateGalleryDialog.svelte`, `lib/templates/`)
 

tests/dom/run.mjs

@@ -30,11 +30,20 @@ try {
   await page.reload({ waitUntil: 'load' });
   await page.waitForSelector('.tiptap', { timeout: 15_000 });
 
+  // What the browser asks before closing the tab: a beforeunload nobody cancels lets it go.
+  const holdsOn = () => page.evaluate(() => {
+    const e = new Event('beforeunload', { cancelable: true });
+    window.dispatchEvent(e);
+    return e.defaultPrevented;
+  });
+  check(!(await holdsOn()), 'an empty document lets the tab close');
+
   // Save on a document with no file behind it settles the format first: the download
   // route cannot read one back from the browser's own dialog.
   await page.evaluate(() => { window.showSaveFilePicker = undefined; });
   await page.click('.tiptap');
   await page.keyboard.type('Format first');
+  check(await holdsOn(), 'a document that was never saved warns before the tab closes');
   await page.keyboard.press(`${MOD}+s`);
   const [firstSave] = await Promise.all([
     page.waitForEvent('download', { timeout: 30_000 }),
@@ -42,6 +51,7 @@ try {
   ]);
   check(firstSave.suggestedFilename().endsWith('.docx'),
     `Ctrl+S on an unsaved document asks for the format (${firstSave.suggestedFilename()})`);
+  check(!(await holdsOn()), 'the saved document lets the tab close again');
 
   // A multi-page corpus document, through the file input (no picker in headless).
   await page.setInputFiles('input.file-input[accept*=".odt"]', join(ROOT, 'tests/corpus/05-breaks.odt'));