acp: Rename assistant::QuoteSelection and support it in agent2 threads (#36628)

Release Notes:

- N/A

assets/keymaps/default-linux.json

@@ -138,7 +138,7 @@
       "find": "buffer_search::Deploy",
       "ctrl-f": "buffer_search::Deploy",
       "ctrl-h": "buffer_search::DeployReplace",
-      "ctrl->": "assistant::QuoteSelection",
+      "ctrl->": "agent::QuoteSelection",
       "ctrl-<": "assistant::InsertIntoEditor",
       "ctrl-alt-e": "editor::SelectEnclosingSymbol",
       "ctrl-shift-backspace": "editor::GoToPreviousChange",
@@ -241,7 +241,7 @@
       "ctrl-shift-i": "agent::ToggleOptionsMenu",
       "ctrl-alt-shift-n": "agent::ToggleNewThreadMenu",
       "shift-alt-escape": "agent::ExpandMessageEditor",
-      "ctrl->": "assistant::QuoteSelection",
+      "ctrl->": "agent::QuoteSelection",
       "ctrl-alt-e": "agent::RemoveAllContext",
       "ctrl-shift-e": "project_panel::ToggleFocus",
       "ctrl-shift-enter": "agent::ContinueThread",