assistant: Polish /workflow and steps UI (#15936)

Fixes #15923
Release Notes:

- Assistant workflow steps can now be applied and reverted directly from
within the assistant panel.

---------

Co-authored-by: Antonio Scandurra <me@as-cii.com>
Co-authored-by: Antonio <antonio@zed.dev>

crates/ui/src/components/button/button_like.rs

@@ -50,6 +50,7 @@ pub enum TintColor {
     Accent,
     Negative,
     Warning,
+    Positive,
 }
 
 impl TintColor {
@@ -73,6 +74,12 @@ impl TintColor {
                 label_color: cx.theme().colors().text,
                 icon_color: cx.theme().colors().text,
             },
+            TintColor::Positive => ButtonLikeStyles {
+                background: cx.theme().status().success_background,
+                border_color: cx.theme().status().success_border,
+                label_color: cx.theme().colors().text,
+                icon_color: cx.theme().colors().text,
+            },
         }
     }
 }
@@ -83,6 +90,7 @@ impl From<TintColor> for Color {
             TintColor::Accent => Color::Accent,
             TintColor::Negative => Color::Error,
             TintColor::Warning => Color::Warning,
+            TintColor::Positive => Color::Success,
         }
     }
 }