feat: Deteksi trigger @mention dan Tab-cycle di input handler

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/controller/input.rs

@@ -7,6 +7,7 @@ use crossterm::event::{KeyCode, KeyEvent, KeyModifiers};
 use crate::app::mode;
 use crate::app::runtime::actions::Action;
 use crate::app::runtime::commands::apply_command;
+use crate::app::state::misc::AutocompleteKind;
 use crate::app::state::rest::AppStateRest;
 use crate::app::state::types::Overlay;
 use crate::controller::command::parse_command;
@@ -247,6 +248,11 @@ pub fn handle_key(key: KeyEvent, state: &mut AppStateRest) -> Vec<Action> {
                     state.input.tab_complete();
                 }
                 state.dirty = true;
+            } else if state.input.autocomplete_kind == AutocompleteKind::FileMention
+                && state.input.autocomplete_visible
+            {
+                state.input.cycle_autocomplete(true);
+                state.dirty = true;
             }
             Vec::new()
         }
@@ -263,6 +269,8 @@ pub fn handle_key(key: KeyEvent, state: &mut AppStateRest) -> Vec<Action> {
             // without requiring an extra Tab press.
             if state.input.buffer.starts_with('/') {
                 state.input.open_autocomplete();
+            } else if state.input.mention_query_at_cursor().is_some() {
+                state.input.open_mention_autocomplete(&state.mention_index.snapshot());
             }
             Vec::new()
         }