feat(options): command line text colour and a fonts folder

Display gets a command line text colour (blank keeps the theme's); it
covers history, prompts and the input, while errors stay red. Files
lists the fonts folder that text resolution searches, so .shx files can
be added by hand; opening it creates it first.

Discussions #1493, #1372

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

src/app/settings.rs

@@ -432,6 +432,8 @@ pub struct UserSettings {
     pub crosshair_color: Option<[u8; 3]>,
     /// Explicit object-snap marker RGB. `None` keeps the automatic colour.
     pub snap_marker_color: Option<[u8; 3]>,
+    /// Explicit command-line text RGB. `None` keeps the theme's.
+    pub command_text_color: Option<[u8; 3]>,
     /// Model-space lineweight preview scale as a percentage.
     pub lineweight_display_scale: i32,
     /// Isometric drafting changes the grid and crosshair to the active axis
@@ -825,6 +827,7 @@ impl Default for UserSettings {
             cursor_type: CursorType::Crosshair,
             crosshair_color: None,
             snap_marker_color: None,
+            command_text_color: None,
             lineweight_display_scale: 100,
             isometric_drafting: false,
             iso_plane: IsoPlane::Left,