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/title_bar/src/application_menu.rs

@@ -12,7 +12,15 @@ use smallvec::SmallVec;
 use ui::{ContextMenu, PopoverMenu, PopoverMenuHandle, Tooltip, prelude::*};
 
 #[cfg(not(target_os = "macos"))]
-actions!(app_menu, [ActivateMenuRight, ActivateMenuLeft]);
+actions!(
+    app_menu,
+    [
+        /// Navigates to the menu item on the right.
+        ActivateMenuRight,
+        /// Navigates to the menu item on the left.
+        ActivateMenuLeft
+    ]
+);
 
 #[cfg(not(target_os = "macos"))]
 #[derive(Clone, Deserialize, JsonSchema, PartialEq, Default, Action)]

crates/title_bar/src/collab.rs

@@ -11,7 +11,17 @@ use workspace::notifications::DetachAndPromptErr;
 
 use crate::TitleBar;
 
-actions!(collab, [ToggleScreenSharing, ToggleMute, ToggleDeafen]);
+actions!(
+    collab,
+    [
+        /// Toggles screen sharing on or off.
+        ToggleScreenSharing,
+        /// Toggles microphone mute.
+        ToggleMute,
+        /// Toggles deafen mode (mute both microphone and speakers).
+        ToggleDeafen
+    ]
+);
 
 fn toggle_screen_sharing(_: &ToggleScreenSharing, window: &mut Window, cx: &mut App) {
     let call = ActiveCall::global(cx).read(cx);

crates/title_bar/src/title_bar.rs

@@ -47,7 +47,17 @@ const MAX_PROJECT_NAME_LENGTH: usize = 40;
 const MAX_BRANCH_NAME_LENGTH: usize = 40;
 const MAX_SHORT_SHA_LENGTH: usize = 8;
 
-actions!(collab, [ToggleUserMenu, ToggleProjectMenu, SwitchBranch]);
+actions!(
+    collab,
+    [
+        /// Toggles the user menu dropdown.
+        ToggleUserMenu,
+        /// Toggles the project menu dropdown.
+        ToggleProjectMenu,
+        /// Switches to a different git branch.
+        SwitchBranch
+    ]
+);
 
 pub fn init(cx: &mut App) {
     TitleBarSettings::register(cx);