feat(protocol): add Paste request type for bracketed-paste events

feat(engine): summarize agent completion progress in UI notifications

feat(main): enable and disable bracketed paste support in terminal

fix(app_config): store API key from file as fallback for Claude provider

refactor(workflow): remove unnecessary card separator in workflow panel

src/ipc/protocol.rs

@@ -45,6 +45,8 @@ pub enum ClientRequest {
         shift: bool,
     },
     Submit(String),
+    /// Bulk-pasted text from a bracketed-paste event.
+    Paste(String),
     Resize(u16, u16),
     Close,
     ScrollUp,