fix(tui): use bare down key to enter child session in subagent view

Match the pattern of up/left/right navigation in subagent view by using
a bare down key instead of <leader>down to navigate into child sessions.
Only the root session view still requires <leader>down.

Author: areyouok

packages/opencode/src/cli/cmd/tui/routes/session/index.tsx

@@ -962,11 +962,24 @@ export function Session() {
       keybind: "session_child_first",
       category: "Session",
       hidden: true,
+      enabled: !session()?.parentID,
       onSelect: (dialog) => {
         moveFirstChild()
         dialog.clear()
       },
     },
+    {
+      title: "Go to child session",
+      value: "session.child.first.subagent",
+      keybind: "session_child_first_subagent",
+      category: "Session",
+      hidden: true,
+      enabled: !!session()?.parentID,
+      onSelect: childSessionHandler((dialog) => {
+        moveFirstChild()
+        dialog.clear()
+      }),
+    },
     {
       title: "Go to parent session",
       value: "session.parent",

packages/opencode/src/cli/cmd/tui/routes/session/subagent-footer.tsx

@@ -128,11 +128,11 @@ export function SubagentFooter() {
               <box
                 onMouseOver={() => setHover("child")}
                 onMouseOut={() => setHover(null)}
-                onMouseUp={() => command.trigger("session.child.first")}
+                onMouseUp={() => command.trigger("session.child.first.subagent")}
                 backgroundColor={hover() === "child" ? theme.backgroundElement : theme.backgroundPanel}
               >
                 <text fg={theme.text}>
-                  Child <span style={{ fg: theme.textMuted }}>{keybind.print("session_child_first")}</span>
+                  Child <span style={{ fg: theme.textMuted }}>{keybind.print("session_child_first_subagent")}</span>
                 </text>
               </box>
             </Show>

packages/opencode/src/config/keybinds.ts

@@ -104,6 +104,7 @@ const KeybindsSchema = Schema.Struct({
   history_previous: keybind("up", "Previous history item"),
   history_next: keybind("down", "Next history item"),
   session_child_first: keybind("<leader>down", "Go to first child session"),
+  session_child_first_subagent: keybind("down", "Go to first child session (from subagent)"),
   session_child_cycle: keybind("right", "Go to next child session"),
   session_child_cycle_reverse: keybind("left", "Go to previous child session"),
   session_parent: keybind("up", "Go to parent session"),