gpui: Store action documentation (#33809)

Closes #ISSUE

Adds a new `documentation` method to actions, that is extracted from doc
comments when using the `actions!` or derive macros.

Additionally, this PR adds doc comments to as many action definitions in
Zed as possible.

Release Notes:

- N/A *or* Added/Fixed/Improved ...

crates/zeta/src/init.rs

@@ -10,7 +10,15 @@ use workspace::Workspace;
 
 use crate::{RateCompletionModal, onboarding_modal::ZedPredictModal};
 
-actions!(edit_prediction, [ResetOnboarding, RateCompletions]);
+actions!(
+    edit_prediction,
+    [
+        /// Resets the edit prediction onboarding state.
+        ResetOnboarding,
+        /// Opens the rate completions modal.
+        RateCompletions
+    ]
+);
 
 pub fn init(cx: &mut App) {
     cx.observe_new(move |workspace: &mut Workspace, _, _cx| {

crates/zeta/src/rate_completion_modal.rs

@@ -9,11 +9,17 @@ use workspace::{ModalView, Workspace};
 actions!(
     zeta,
     [
+        /// Rates the active completion with a thumbs up.
         ThumbsUpActiveCompletion,
+        /// Rates the active completion with a thumbs down.
         ThumbsDownActiveCompletion,
+        /// Navigates to the next edit in the completion history.
         NextEdit,
+        /// Navigates to the previous edit in the completion history.
         PreviousEdit,
+        /// Focuses on the completions list.
         FocusCompletions,
+        /// Previews the selected completion.
         PreviewCompletion,
     ]
 );

crates/zeta/src/zeta.rs

@@ -72,7 +72,13 @@ const MAX_EVENT_TOKENS: usize = 500;
 /// Maximum number of events to track.
 const MAX_EVENT_COUNT: usize = 16;
 
-actions!(edit_prediction, [ClearHistory]);
+actions!(
+    edit_prediction,
+    [
+        /// Clears the edit prediction history.
+        ClearHistory
+    ]
+);
 
 #[derive(Copy, Clone, Default, Debug, PartialEq, Eq, Hash)]
 pub struct InlineCompletionId(Uuid);