split: click a pane to drive it (not just Tab) + spell it out in the status

The sync direction follows the FOCUSED pane, but that was only discoverable via
Tab. Add on_descendant_focus: in split, focusing a pane (Tab or a mouse click)
makes it the leading/driver pane and re-syncs — so clicking into the pseudocode
and cursoring around now drives the listing, matching intuition (previously a
click focused the widget but left _active — and thus the sync direction —
pointing at the other pane). The split status now ends with "(Tab/click: drive
<other pane>)" so it's obvious.

Pilot split_view: clicking the pseudocode pane makes it the driver (17/17).

1 files changed, 7 insertions, 0 deletions

diff --git a/tests/test_scenarios.py b/tests/test_scenarios.py
index 3401645..7d9f3b7 100644
--- a/tests/test_scenarios.py
+++ b/tests/test_scenarios.py
@@ -415,6 +415,13 @@ async def s_split_view(c: Ctx):
     await c.pause(0.1)
     c.check("Tab again focuses the listing pane", app._active == "listing",
             f"active={app._active}")
+    # a mouse click on the other pane also makes it the driver (not just Tab)
+    await c.pilot.click(DecompView, offset=(10, 5))
+    await c.pause(0.15)
+    c.check("clicking the pseudocode pane makes it the driver",
+            app._active == "decomp", f"active={app._active}")
+    await c.press("tab")  # restore listing as the driver
+    await c.pause(0.1)
     # navigation in split keeps BOTH panes on the (new) function
     nf = c.find_func(lambda f: f.addr != app._cur.ea and f.size > 80)
     if nf is not None: