feat(dashboard): focus right pane on Enter re-attach (in tmux)

The Enter key on a focused agents-pane row is the operator's
explicit "I want to interact with this agent" signal — after
respawning the right pane with claude, move tmux's keyboard
focus to that pane so the operator can start typing
immediately. Without this, every Enter required a manual tmux
nav (C-b →) to actually use the session.

Mechanics:

  - `_attach_in_tmux` gains `focus_right_pane: bool = False`.
  - When True, runs `tmux select-pane -t <pane_id>` after the
    respawn.
  - `_attach_to_bottle` (the Enter handler's helper) passes
    True.
  - Other callers (new-agent flow, stop's auto-attach) leave
    it False so the operator stays in the dashboard for
    follow-up navigation.

`_tmux_select_pane` is a small subprocess wrapper, best-effort
on failure.

claude_bottle/cli/dashboard.py

@@ -995,12 +995,19 @@ def _attach_in_tmux(
     *,
     resume: bool,
     tmux_state: dict,
+    focus_right_pane: bool = False,
 ) -> str:
     """Spawn / respawn the right pane with `bottle`'s claude
     session. Mutates `tmux_state` ({'pane_id': str|None,
     'slug': str|None}) so the main loop can track which slug is
     in the right pane (used by the agents-pane indicator + the
-    explicit-stop hook)."""
+    explicit-stop hook).
+
+    `focus_right_pane=True` runs `tmux select-pane` after the
+    respawn so the operator is dropped into claude immediately.
+    The Enter re-attach key passes this; passive paths (the
+    auto-attach after a stop) leave it False so the operator
+    stays in the dashboard pane."""
     docker_argv = bottle.claude_docker_argv(
         _claude_runtime_args(resume=resume),
     )
@@ -1011,9 +1018,24 @@ def _attach_in_tmux(
         # operator still gets a session.
         return _attach_via_handoff(stdscr, bottle, slug, resume=resume)
     tmux_state["slug"] = slug
+    if focus_right_pane:
+        _tmux_select_pane(pane_id)
     return f"[{slug}] in right pane"
 
 
+def _tmux_select_pane(pane_id: str) -> None:
+    """`tmux select-pane -t <id>` — moves tmux's keyboard focus
+    to the pane. Best-effort; failure is silent (logged only via
+    subprocess's stderr, which we suppress)."""
+    try:
+        subprocess.run(
+            ["tmux", "select-pane", "-t", pane_id],
+            capture_output=True, text=True, check=False,
+        )
+    except FileNotFoundError:
+        pass
+
+
 def _attach_to_bottle(
     stdscr: "curses._CursesWindow",
     bottle,
@@ -1028,8 +1050,13 @@ def _attach_to_bottle(
     blocks until the operator exits claude. Re-attach always uses
     `--continue` — first attach happens via `_new_agent_flow`."""
     if _in_tmux() and tmux_state is not None:
+        # Enter re-attach is an explicit "I want to interact with
+        # this agent" signal — move tmux focus to the right pane
+        # so keypresses land in claude instead of the dashboard.
         return _attach_in_tmux(
-            stdscr, bottle, slug, resume=True, tmux_state=tmux_state,
+            stdscr, bottle, slug,
+            resume=True, tmux_state=tmux_state,
+            focus_right_pane=True,
         )
     return _attach_via_handoff(stdscr, bottle, slug, resume=True)