Keep the project picker reachable while the rail is collapsed

The picker was hidden outright at 54px, on the grounds that a combo box there
could only show a stub of a name. True, but it left the collapsed rail with no
way to change project at all — and the audit page's own inventory of the 11
collapsible controls says the rail's fold "giữ nguyên toàn bộ".

A folder QToolButton stands in for it: same items, and choosing one moves the
combo, so _on_rail_project_pick stays the single code path. Its tooltip carries
the current project name, which the combo could not have shown anyway. It
matches the ＋ button's width and drops its menu arrow — at 42px the arrow
would take a third of the row to say nothing.

check_nav now collapses the rail and requires a reachable picker whose menu
matches the combo item for item, then picks a row and asserts the project
actually changed. Hiding the button fails it.

15/15 checkers pass.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tools/check_nav.py

@@ -289,6 +289,37 @@ def main() -> int:
     print(f"provider dang chon : {win.provider_combo.currentText()!r}")
     print(f"tai khoan          : {win.account_lbl.text()!r}")
 
+    # Collapsing the rail must not take the project picker away with it: at
+    # 54px the combo cannot show a name, so a folder button stands in for it.
+    if not win._nav_collapsed:
+        win._toggle_nav()
+        app.processEvents()
+    mini = getattr(win, "nav_project_btn", None)
+    if mini is None or mini.isHidden():
+        fails.append("thu gon rail xong khong con cach nao doi project")
+    else:
+        mini.menu().aboutToShow.emit()
+        app.processEvents()
+        menu_items = [a.text() for a in mini.menu().actions()]
+        combo_items = [win.nav_project.itemText(i)
+                       for i in range(win.nav_project.count())]
+        if menu_items != combo_items:
+            fails.append(f"menu project khi thu gon lech voi combo: "
+                         f"{menu_items} vs {combo_items}")
+        elif len(menu_items) > 1:
+            before = win.workspace.selected_project_id()
+            # Any row but the one already selected, or nothing would change.
+            row = (win.nav_project.currentIndex() + 1) % len(menu_items)
+            mini.menu().actions()[row].trigger()
+            app.processEvents()
+            after = win.workspace.selected_project_id()
+            if after == before:
+                fails.append("chon project tu menu thu gon khong doi project")
+            else:
+                print(f"doi project khi thu gon: {before} -> {after}")
+    win._toggle_nav()
+    app.processEvents()
+
     print()
     print(f"tong dong dieu huong: {n_total} + nut Cai dat")
     if fails: