Fix IndentGuides story (#32781)

This PR updates the `Model` to `Entity` also fixes the
`IndentGuidesStory`. In this
[commit](6fca1d2b0b),
`Entity<T>` replaces `View<T>`/`Model<T>`.

Other than this, I noticed the storybook fails on my MacOS and Ubuntu,
see error below

```
thread 'main' panicked at crates/gpui/src/colors.rs:99:15:
called `Result::unwrap()` on an `Err` value: no state of type gpui::colors::GlobalColors exists
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```

This was resolved by explicitly specifying `GlobalColors` in Storybook.

Release Notes:

- N/A

crates/storybook/src/storybook.rs

@@ -9,7 +9,9 @@ use std::sync::Arc;
 use clap::Parser;
 use dialoguer::FuzzySelect;
 use gpui::{
-    AnyView, App, Bounds, Context, Render, Window, WindowBounds, WindowOptions, div, px, size,
+    AnyView, App, Bounds, Context, Render, Window, WindowBounds, WindowOptions,
+    colors::{Colors, GlobalColors},
+    div, px, size,
 };
 use log::LevelFilter;
 use project::Project;
@@ -68,6 +70,8 @@ fn main() {
     gpui::Application::new().with_assets(Assets).run(move |cx| {
         load_embedded_fonts(cx).unwrap();
 
+        cx.set_global(GlobalColors(Arc::new(Colors::default())));
+
         let http_client = ReqwestClient::user_agent("zed_storybook").unwrap();
         cx.set_http_client(Arc::new(http_client));