fix(tui): change transcript 'g' scroll to vim-style 'gg' double-tap

A single bare 'g' with an empty composer was hijacked as a scroll-to-top
command, preventing users from typing 'g' as the first character of a message.
The transcript would jump to line 0 instead of inserting 'g' into the composer.

Change to a vim-style 'gg' double-tap: first 'g' arms transcript_pending_g,
second 'g' executes the scroll. Any other character input, Enter, or Escape
resets the pending flag so a stray 'g' during composition arms without
scrolling.

Also adds transcript_pending_g field to App struct (default false).

crates/tui/src/tui/app.rs

@@ -878,6 +878,12 @@ pub struct App {
     /// Esc primes, second Esc opens the live-transcript overlay scoped to
     /// previous user messages so the user can rewind a turn.
     pub backtrack: crate::tui::backtrack::BacktrackState,
+    /// Pending 'gg' second keystroke for vim-style jump-to-top of the
+    /// transcript. Set by the first bare 'g' with an empty composer and
+    /// consumed on the second 'g' to scroll to line 0. Any other
+    /// navigation key resets it, so typing 'g' as the first character
+    /// of a message only arms this flag without scrolling.
+    pub transcript_pending_g: bool,
     /// Current session ID for auto-save updates
     pub current_session_id: Option<String>,
     /// Metadata-only registry of large tool outputs produced in this session.
@@ -1465,6 +1471,7 @@ impl App {
             },
             view_stack: ViewStack::new(),
             backtrack: crate::tui::backtrack::BacktrackState::new(),
+            transcript_pending_g: false,
             current_session_id: None,
             session_artifacts: Vec::new(),
             trust_mode: initial_mode == AppMode::Yolo,

crates/tui/src/tui/ui.rs

@@ -2391,7 +2391,9 @@ async fn run_event_loop(
                     app.mention_menu_hidden = true;
                     app.mention_menu_selected = 0;
                 }
-                KeyCode::Esc => match next_escape_action(app, slash_menu_open) {
+                KeyCode::Esc => {
+                    app.transcript_pending_g = false;
+                    match next_escape_action(app, slash_menu_open) {
                     EscapeAction::CloseSlashMenu => {
                         // A popup-style action wins over backtrack — clear
                         // any prime so a stale Primed state can't jump us
@@ -2460,7 +2462,8 @@ async fn run_event_loop(
                             }
                         }
                     }
-                },
+                }
+            },
                 KeyCode::Up if key.modifiers.contains(KeyModifiers::SUPER) => {
                     app.scroll_up(app.viewport.last_transcript_visible.max(3));
                 }
@@ -2572,10 +2575,20 @@ async fn run_event_loop(
                 KeyCode::Char('g')
                     if key.modifiers.is_empty() && app.input.is_empty() && !slash_menu_open =>
                 {
-                    if let Some(anchor) =
+                    // Vim-style 'gg' — double-tap 'g' to jump to top.
-                        TranscriptScroll::anchor_for(app.viewport.transcript_cache.line_meta(), 0)
+                    // First 'g' arms the pending flag; second executes the scroll.
-                    {
+                    // This prevents a single 'g' (the first letter of a message)
-                        app.viewport.transcript_scroll = anchor;
+                    // from hijacking the transcript scroll.
+                    if app.transcript_pending_g {
+                        if let Some(anchor) = TranscriptScroll::anchor_for(
+                            app.viewport.transcript_cache.line_meta(),
+                            0,
+                        ) {
+                            app.viewport.transcript_scroll = anchor;
+                        }
+                        app.transcript_pending_g = false;
+                    } else {
+                        app.transcript_pending_g = true;
                     }
                 }
                 KeyCode::Char('G')
@@ -2675,6 +2688,7 @@ async fn run_event_loop(
                     }
                 }
                 KeyCode::Enter => {
+                    app.transcript_pending_g = false;
                     // #573: when the user typed a slash-command prefix that
                     // the popup is matching (e.g. `/mo` → `/model`), Enter
                     // should run the *highlighted match* rather than
@@ -2986,6 +3000,11 @@ async fn run_event_loop(
                     // absorb — Visual mode not yet fully implemented
                 }
                 KeyCode::Char(c) => {
+                    // Any typed character after a pending 'g' means the user
+                    // is composing a message, not navigating — disarm the
+                    // 'gg' double-tap so the next bare 'g' on an empty
+                    // composer starts a new sequence.
+                    app.transcript_pending_g = false;
                     app.insert_char(c);
                 }
                 _ => {}