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/theme.rs

@@ -266,8 +266,6 @@ pub struct Tokens {
     pub app_bar_text: Color32,
     /// A hovered tab on the application bar (keeps `app_bar_text` readable).
     pub app_bar_hover: Color32,
-    /// Outline of the inactive tabs on the application bar, so neighbouring tabs stay apart.
-    pub app_bar_tab_edge: Color32,
     /// Timeline items: normal and failed.
     pub timeline_item: Color32,
     pub timeline_item_error: Color32,