Title bar: inactive tabs without outlines, File menu, Help on the right (#1277)

* Title bar: inactive tabs without outlines, File menu, Help on the right

Inactive tabs go back to the plain bar colour (the Home tab's readable
hover stays). The separate Home button and theme toggle are gone: Home is
a tab and the theme is in Preferences. The folder icon becomes a File text
menu, Save moves into it (Ctrl+S unchanged), and Help sits on the right
next to Report a bug. Tabs start right after File, Undo and Redo.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Title bar: File button hover uses the app bar hover token

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/ui-egui/src/documents.rs

@@ -455,7 +455,7 @@ pub fn tabs(app: &mut SolveApp, ui: &mut egui::Ui, r: Rect, x0: f32, x1: f32) {
 }
 
 /// One tab of the strip: the active tab takes the toolbar's colour and runs into it; the others
-/// sit on the application bar with a faint outline (no bottom edge) so neighbours stay apart.
+/// sit on the application bar, lighter while hovered.
 fn tab_shape(painter: &egui::Painter, t: &Tokens, r: Rect, active: bool, hovered: bool) {
     let corners = egui::CornerRadius { nw: 5, ne: 5, sw: 0, se: 0 };
     let fill = if active {
@@ -466,11 +466,6 @@ fn tab_shape(painter: &egui::Painter, t: &Tokens, r: Rect, active: bool, hovered
         t.app_bar
     };
     painter.rect_filled(r, corners, fill);
-    if !active {
-        // Drawn past the bottom and clipped, so only the top and the sides show.
-        let outline = Rect::from_min_max(r.min, pos2(r.max.x, r.max.y + 2.0));
-        painter.with_clip_rect(r).rect_stroke(outline, corners, Stroke::new(1.0, t.app_bar_tab_edge), egui::StrokeKind::Inside);
-    }
 }
 
 /// Which tabs the strip shows in `room` points: (first, how many, tab width). Tabs shrink to
@@ -629,10 +624,9 @@ mod tests {
     }
 
     /// The tabs sit on the dark application bar in both themes: a hovered tab (the Home tab
-    /// included) keeps the bar's light text readable, and an inactive tab is outlined so
-    /// neighbouring tabs stay apart.
+    /// included) keeps the bar's light text readable, and no tab is outlined.
     #[test]
-    fn title_bar_tabs_are_outlined_and_keep_their_text_readable_on_hover() {
+    fn title_bar_tabs_keep_their_text_readable_on_hover() {
         fn luminance(c: Color32) -> f32 {
             let c = egui::Rgba::from(c);
             0.2126 * c.r() + 0.7152 * c.g() + 0.0722 * c.b()
@@ -662,11 +656,7 @@ mod tests {
                     let (hi, lo) = (luminance(t.app_bar_text).max(luminance(bg)), luminance(t.app_bar_text).min(luminance(bg)));
                     assert!((hi + 0.05) / (lo + 0.05) >= 4.5, "text on a tab (hovered: {hovered}) must stay readable: {bg:?} {t:?}");
                 }
-                let outline = rects.iter().find(|(rect, _)| rect.stroke.width > 0.0);
-                assert_eq!(outline.is_some(), !active, "only inactive tabs are outlined (active: {active})");
-                if let Some((rect, clip)) = outline {
-                    assert!(rect.rect.bottom() > r.bottom() && clip.bottom() <= r.bottom(), "the outline has no bottom edge");
-                }
+                assert!(rects.iter().all(|(rect, _)| rect.stroke.width == 0.0), "tabs have no outline (active: {active})");
             }
         }
     }