Add title pages, standard manuscript format and collapsible panels

Five changes to the export and the window chrome:

* Manuscript details gains a contact field and a "Begin exports with a
  title page" option: the title, the author beneath it, and the contact
  details beneath that, laid out line for line as typed. A chapters +
  master export puts the title page on the master, not on each chapter.

* "Standard manuscript format" lays an export out the way an agent or an
  editor expects a submission: 12pt Courier, double-spaced, half-inch
  first-line indents, a Surname / Title / page header on every page but
  the title page, chapters opening a third of the way down, and `---`
  rendered as the conventional centred `#` scene break. The title page
  becomes the submission kind, with contact top-left and an approximate
  word count top-right. Off by default; margins were already the
  standard 1in on US Letter and are unchanged either way.

* A folder button beside Export ODT opens the project folder in the file
  manager -- the enclosing git work tree, including one still awaiting
  confirmation, since showing a folder is a smaller question than
  choosing which repository to commit to.

* The toolbar and the file list each collapse, from the pair of buttons
  at the right of the menu bar or from the View menu, and Ctrl+D folds
  both away together for distraction-free writing. Both choices persist.

* The editor sizes to its viewport instead of a fixed 30 rows, so the
  height a folded panel gives back reaches the page rather than leaving
  grey space below the text box that did not even take focus.

Two traps worth recording. ODF's style:master-page-name is inherited,
and any paragraph style carrying one forces a page break before every
paragraph that uses it -- a four-line contact block came out as four
pages until Contact_20_Line stopped inheriting from Contact_20_Block;
a test now pins which styles may carry one. And the status bar shares
a function with the toolbar, so guarding that function's top rather
than the top panel alone silently took the word counts away with it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GYSGPDwkSzhm4qLqjCbqxU

src/app/editor.rs

@@ -82,11 +82,20 @@ impl App {
                     self.apply_field_completion(ui.ctx(), &field);
                 }
 
+                // Fill the viewport rather than a fixed number of rows, so the
+                // height handed back by a folded toolbar or file list reaches
+                // the page instead of leaving grey space under the editor.
+                // Measured against the *unzoomed* row height because that is
+                // what `desired_rows` is multiplied by, whatever the layouter
+                // then draws at.
+                let row_h = ui.text_style_height(&egui::TextStyle::Monospace).max(1.0);
+                let rows = (ui.available_height() / row_h).floor().max(10.0) as usize;
+
                 let output = egui::TextEdit::multiline(&mut self.buffer)
                     .id(egui::Id::new(EDITOR_ID))
                     .code_editor()
                     .desired_width(f32::INFINITY)
-                    .desired_rows(30)
+                    .desired_rows(rows)
                     .layouter(&mut layouter)
                     .show(ui);
                 if output.response.changed() {