macOS: Selection for Find feature

Adds the `selection_for_search` action, with Cmd+E keybind by default.
This action inputs the currently selected text into the search
field without changing focus, matching standard macOS behavior.

src/apprt/action.zig

@@ -316,6 +316,9 @@ pub const Action = union(Key) {
     /// Start the search overlay with an optional initial needle.
     start_search: StartSearch,
 
+    /// Input the selected text into the search field.
+    selection_for_search: SelectionForSearch,
+
     /// End the search overlay, clearing the search state and hiding it.
     end_search,
 
@@ -389,6 +392,7 @@ pub const Action = union(Key) {
         show_on_screen_keyboard,
         command_finished,
         start_search,
+        selection_for_search,
         end_search,
         search_total,
         search_selected,
@@ -914,3 +918,18 @@ pub const SearchSelected = struct {
         };
     }
 };
+
+pub const SelectionForSearch = struct {
+    text: [:0]const u8,
+
+    // Sync with: ghostty_action_selection_for_search_s
+    pub const C = extern struct {
+        text: [*:0]const u8,
+    };
+
+    pub fn cval(self: SelectionForSearch) C {
+        return .{
+            .text = self.text.ptr,
+        };
+    }
+};