feat(ui): ribbon collapse-mode selector + start-page recent controls

Ribbon:
- A ▾ selector at the right of the tab row picks the tool-panel density —
  Auto (size to window), Full, Compact, or Collapsed. The choice is persisted.
  It hides itself when the tool row is already tight, giving the cramped tab
  row its space back.

Start page:
- The Recent Documents card is restyled to match the Supporters card
  (rounded corners, 20px padding, matching title + colours).
- Its scrollbar no longer sits on top of the row ✕ remove buttons (a gutter
  is reserved).
- A footer control sets how many recent files to keep: [-] an editable count
  [+] with the max shown. Typing applies on Enter; an over-max entry snaps to
  the max. The limit is persisted and enforced on load and on every open.
- The "Support on Patreon" heart is now the SVG icon instead of a font glyph.

Config:
- Add a shared `config::config_dir()` helper; the recent-files and status-bar
  stores now go through it instead of each re-deriving the path. New minus.svg
  icon for the stepper.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/ui/ribbon/mod.rs

@@ -6,7 +6,7 @@
 //
 // Dropdown items within a group are collected into columns of 3 rows.
 
-use std::sync::atomic::{AtomicU32, Ordering};
+use std::sync::atomic::{AtomicBool, AtomicU32, Ordering};
 use std::sync::Arc;
 
 use rustc_hash::FxHashMap as HashMap;
@@ -24,7 +24,8 @@ mod widgets;
 use widgets::{StyleContext, *};
 mod collapse;
 use collapse::{CollapsePanels, Panel};
-use crate::ui::wrap_bar::{WrapBar, WrapFlow};
+pub use collapse::CollapseMode;
+use crate::ui::wrap_bar::{PosReport, WrapBar, WrapFlow};
 
 // ── Ribbon state ───────────────────────────────────────────────────────────
 
@@ -70,6 +71,11 @@ pub struct Ribbon {
     /// panel is collapsed). Written by `CollapsePanels`, read when anchoring
     /// dropdowns below the ribbon.
     tool_bar_h: Arc<AtomicU32>,
+    /// User-chosen panel density (persisted). `Auto` sizes by window width.
+    collapse_mode: CollapseMode,
+    /// Set by `CollapsePanels` when the tool row is in its tight state; the mode
+    /// selector hides itself then to give the cramped tab row its space back.
+    collapse_tight: Arc<AtomicBool>,
 }
 
 /// Per-layer display data shown in the ribbon layer dropdown.
@@ -155,9 +161,17 @@ impl Ribbon {
             active_table_style: String::new(),
             tab_bar_h: Arc::new(AtomicU32::new(28.0f32.to_bits())),
             tool_bar_h: Arc::new(AtomicU32::new(TOOL_BAR_H.to_bits())),
+            collapse_mode: CollapseMode::load(),
+            collapse_tight: Arc::new(AtomicBool::new(false)),
         }
     }
 
+    /// Change the tool-panel density and persist the choice.
+    pub fn set_collapse_mode(&mut self, mode: CollapseMode) {
+        self.collapse_mode = mode;
+        mode.save();
+    }
+
     /// Current tab-bar height as last measured by the `WrapBar` widget.
     fn tab_bar_height(&self) -> f32 {
         f32::from_bits(self.tab_bar_h.load(Ordering::Relaxed))
@@ -436,16 +450,41 @@ impl Ribbon {
             .min_spacing_x(0.0)
             .row_h(28.0);
 
-        let tab_bar = container(
+        // Panel-density selector, pinned to the right edge of the tab row: a bare
+        // ▾ button that opens a list of modes (see `dropdown_overlay`). `Auto`
+        // sizes panels to the window; the others force one density. The choice is
+        // persisted (see `Ribbon::set_collapse_mode`). It hides itself once the
+        // tool row is tight, giving the cramped tab row its space back.
+        let dd_open = self.open_dropdown.as_deref() == Some(COLLAPSE_MODE_ID);
+        let mode_btn = button(crate::ui::icons::arrow_down(10.0, ARROW_COLOR))
+            .on_press(Message::ToggleRibbonDropdown(COLLAPSE_MODE_ID.to_string()))
+            .style(move |_: &Theme, status| top_hist_btn_style(true, dd_open, status))
+            .height(24)
+            .padding([2, 8]);
+        let mode_dd = PosReport::new(COLLAPSE_MODE_ID, mode_btn);
+
+        let mut tab_row = row![container(
             WrapBar::new(lead.into(), tabs.into())
                 .spacing(6.0)
                 .report_height(self.tab_bar_h.clone()),
         )
-        .style(|_: &Theme| container::Style {
-            background: Some(Background::Color(TOPBAR_BG)),
-            ..Default::default()
-        })
-        .width(Length::Fill);
+        .width(Length::Fill)]
+        .spacing(6.0)
+        .align_y(iced::Center);
+        if !self.collapse_tight.load(Ordering::Relaxed) {
+            tab_row = tab_row.push(mode_dd);
+        }
+
+        let tab_bar = container(tab_row)
+            .style(|_: &Theme| container::Style {
+                background: Some(Background::Color(TOPBAR_BG)),
+                ..Default::default()
+            })
+            .padding(Padding {
+                right: 6.0,
+                ..Padding::ZERO
+            })
+            .width(Length::Fill);
 
         // ── Tool area ─────────────────────────────────────────────────────
         let effective_active = if !is_paper
@@ -572,6 +611,8 @@ impl Ribbon {
                     .collect();
                 CollapsePanels::new(panels, self.collapsed_open.clone(), TOOL_BAR_H, BORDER_DARK)
                     .report_height(self.tool_bar_h.clone())
+                    .report_tight(self.collapse_tight.clone())
+                    .mode(self.collapse_mode)
                     .into()
             } else {
                 text("").into()
@@ -651,6 +692,56 @@ impl Ribbon {
             return Some(dropdown_backdrop(positioned));
         }
 
+        if open_id == COLLAPSE_MODE_ID {
+            const W: f32 = 150.0;
+            let current = self.collapse_mode;
+            let rows: Vec<Element<Message>> = CollapseMode::ALL
+                .iter()
+                .map(|&m| {
+                    let mark: Element<Message> = if m == current {
+                        crate::ui::icons::tinted(crate::ui::icons::CHECK, 11.0, CHECK_COLOR)
+                    } else {
+                        iced::widget::Space::new().width(0).into()
+                    };
+                    button(
+                        row![
+                            container(mark).width(Length::Fixed(16.0)),
+                            text(m.label()).size(11).color(LABEL_ON),
+                        ]
+                        .spacing(4)
+                        .align_y(iced::Center),
+                    )
+                    .on_press(Message::SetRibbonCollapseMode(m))
+                    .style(|_: &Theme, status| button::Style {
+                        background: Some(Background::Color(match status {
+                            button::Status::Hovered | button::Status::Pressed => ROW_HOVER,
+                            _ => Color::TRANSPARENT,
+                        })),
+                        ..Default::default()
+                    })
+                    .width(Fill)
+                    .padding([5, 10])
+                    .into()
+                })
+                .collect();
+
+            let panel = container(column(rows))
+                .style(|_: &Theme| container::Style {
+                    background: Some(Background::Color(PANEL_BG)),
+                    border: Border {
+                        color: PANEL_BORDER,
+                        width: 1.0,
+                        radius: 3.0.into(),
+                    },
+                    ..Default::default()
+                })
+                .width(Length::Fixed(W));
+
+            let (align_right, h_pad, top) = self.dd_anchor(open_id, W, win.0);
+            let positioned = position_ribbon_dropdown(panel.into(), align_right, h_pad, top);
+            return Some(dropdown_backdrop(positioned));
+        }
+
         if open_id == LAYER_COMBO_ID {
             return self.layer_combo_overlay(win);
         }