tlc: Sprint 2 B8 — Input widget uses theme tokens by default

Input widget colors no longer hardcoded to Color::White / Blue /
Yellow. New instances use Color::Reset as a sentinel meaning
'use the theme token', and render() falls back to:
  - fg: theme.foreground
  - bg: theme.background
  - cursor_color: theme.warning

Callers that explicitly call .fg() / .bg() / .cursor_color() still
override the sentinel — existing API surface preserved.

Changes:
  - input.rs::Input::new() defaults fg/bg/cursor_color to Color::Reset
  - input.rs::Input::render() resolves Reset → theme token
  - New pub fn cursor_color(c) builder (was missing; .fg/.bg existed)

Tests (2 new in widget::input::tests):
  - default_colors_are_reset_sentinel
  - explicit_color_overrides_reset_sentinel

Total: 1268 passing (was 1266; +2 new).

local/recipes/tui/tlc/source/src/widget/input.rs

@@ -67,9 +67,13 @@ impl Input {
             placeholder: None,
             candidates: Vec::new(),
             ac_index: None,
-            fg: Color::White,
-            bg: Color::Blue,
-            cursor_color: Color::Yellow,
+            // Defaults are `Color::Reset` so render() falls back to
+            // theme tokens (theme.foreground / theme.background /
+            // theme.warning for the cursor). Callers can still
+            // override with .fg() / .bg() / .cursor_color().
+            fg: Color::Reset,
+            bg: Color::Reset,
+            cursor_color: Color::Reset,
         }
     }
 
@@ -123,6 +127,13 @@ impl Input {
         self
     }
 
+    /// Set the cursor marker color.
+    #[must_use]
+    pub fn cursor_color(mut self, c: Color) -> Self {
+        self.cursor_color = c;
+        self
+    }
+
     /// Current text.
     #[must_use]
     pub fn value(&self) -> &str {
@@ -305,8 +316,14 @@ impl Input {
         } else {
             self.text.clone()
         };
+        // Apply theme defaults when the Input was not customized via
+        // the builder methods. `Color::Reset` is the sentinel meaning
+        // "use the theme token".
+        let fg = if self.fg == Color::Reset { theme.foreground } else { self.fg };
+        let bg = if self.bg == Color::Reset { theme.background } else { self.bg };
+        let cursor_color = if self.cursor_color == Color::Reset { theme.warning } else { self.cursor_color };
         let style = if self.focused {
-            Style::default().fg(self.fg).bg(self.bg)
+            Style::default().fg(fg).bg(bg)
         } else {
             Style::default().fg(theme.hidden)
         };
@@ -320,7 +337,7 @@ impl Input {
             .border_style(style)
             .title(Span::styled(
                 title,
-                Style::default().fg(self.fg).add_modifier(Modifier::BOLD),
+                Style::default().fg(fg).add_modifier(Modifier::BOLD),
             ));
         let p = Paragraph::new(display).style(style).block(block);
         frame.render_widget(p, area);
@@ -332,7 +349,7 @@ impl Input {
                 let marker = Paragraph::new(Span::styled(
                     "|",
                     Style::default()
-                        .fg(self.cursor_color)
+                        .fg(cursor_color)
                         .add_modifier(Modifier::SLOW_BLINK),
                 ));
                 frame.render_widget(marker, Rect::new(cursor_x, inner.y, 1, 1));
@@ -508,4 +525,24 @@ mod tests {
         assert!(i.handle_key(Key::ctrl('d')));
         assert_eq!(i.value(), "bc");
     }
+
+    #[test]
+    fn default_colors_are_reset_sentinel() {
+        // The default fg/bg/cursor_color fields are Color::Reset so
+        // render() can fall back to theme tokens. Callers that
+        // explicitly set colors via .fg() / .bg() / .cursor_color()
+        // override the sentinel.
+        let i = Input::new();
+        assert_eq!(i.fg, Color::Reset);
+        assert_eq!(i.bg, Color::Reset);
+        assert_eq!(i.cursor_color, Color::Reset);
+    }
+
+    #[test]
+    fn explicit_color_overrides_reset_sentinel() {
+        let i = Input::new().fg(Color::Red).bg(Color::Green).cursor_color(Color::Magenta);
+        assert_eq!(i.fg, Color::Red);
+        assert_eq!(i.bg, Color::Green);
+        assert_eq!(i.cursor_color, Color::Magenta);
+    }
 }