feat(claudbg-mfpd): Esc/Backspace returns to session transcript from agent transcript

When on SubagentTranscript, Esc or Backspace now goes back to the parent
session's Transcript view (lazy-reloads entries) instead of jumping all
the way to the session list. Transcript → session list path unchanged.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.beans/claudbg-mfpd--tui-navigate-back-to-main-session-transcript-from.md

@@ -1,10 +1,17 @@
 ---
 # claudbg-mfpd
 title: 'TUI: navigate back to main session transcript from agent transcript'
-status: todo
+status: completed
 type: feature
+priority: normal
 created_at: 2026-03-31T23:45:12Z
-updated_at: 2026-03-31T23:45:12Z
+updated_at: 2026-04-01T05:55:11Z
 ---
 
 There is currently no way to navigate back to the main session transcript after drilling into an agent transcript. Add a keybinding (e.g. Backspace or Escape) to return to the parent session view.
+
+## Summary of Changes
+
+Added `go_back_to_transcript(parent_session_id)` to `AppState` in `state.rs`: transitions to `Screen::Transcript { session_id: parent_session_id }`, clears transcript entries (to trigger lazy-reload), and leaves `subagents` intact (they belong to the parent session).
+
+Changed the Esc/Backspace arm in `handle_transcript_event` (`transcript.rs`) to be context-aware: when on `SubagentTranscript`, calls `go_back_to_transcript` to return to the parent session view; when on `Transcript`, calls `go_back` to return to the session list. Backspace is added as a second binding alongside Escape.

src/tui/screens/transcript.rs

@@ -551,9 +551,17 @@ pub fn handle_transcript_event(event: Event, state: &mut AppState) -> bool {
             };
             true
         }
-        // Navigate back to the session list.
+        // Navigate back: from SubagentTranscript → parent session transcript;
-        KeyCode::Esc => {
+        // from Transcript → session list.
-            state.go_back();
+        KeyCode::Esc | KeyCode::Backspace => {
+            if let crate::tui::state::Screen::SubagentTranscript {
+                parent_session_id, ..
+            } = state.screen.clone()
+            {
+                state.go_back_to_transcript(&parent_session_id);
+            } else {
+                state.go_back();
+            }
             true
         }
         // Show quit dialog (don't exit immediately on transcript screen).

src/tui/state.rs

@@ -300,6 +300,27 @@ impl AppState {
         self.focus = Focus::ChatLog;
     }
 
+    /// Return to the parent session's transcript from a sub-agent transcript.
+    ///
+    /// Clears transcript entries so the lazy-loader will reload the parent
+    /// session's content.  The sub-agents list is left intact because it
+    /// belongs to the parent session and will still be accurate.
+    pub fn go_back_to_transcript(&mut self, parent_session_id: &str) {
+        self.screen = Screen::Transcript {
+            session_id: parent_session_id.to_string(),
+        };
+        self.transcript_entries.clear();
+        self.transcript_scroll = 0;
+        self.transcript_h_scroll = 0;
+        self.search_input.clear();
+        self.search_active.clear();
+        self.search_match_lines.clear();
+        self.search_current_match = 0;
+        self.pending_g = false;
+        self.focus = Focus::ChatLog;
+        // Leave subagents intact — they belong to the parent session.
+    }
+
     /// Return to the session-list screen.
     ///
     /// Clears transcript and sub-agent data.  The session list and the