feat(gui): one-click Close in its own bottom sidebar section

Close is now a direct shutdown trigger: visiting the Close page (the
sidebar entry) fires shutdown_app() immediately — no confirm step, no
intermediate body. The farewell overlay paints and os._exit(0) lands
~1s later from a daemon thread.

Layout: Close moved into its own bottom-of-sidebar section so the
destructive action is visually separated from Account/Activate.

- New shutdown_app() in components/_legacy.py replaces quit_button.
  os._exit thread is skipped when "pytest" is in sys.modules so the
  test suite doesn't suicide on rendering 99_Close.
- pages/99_Close.py shrinks to set_page_config + chrome + shutdown_app.
- app.py nav grows a new "Close" section header (new
  nav.section_close key in en/es packs) pinned at the bottom of the
  navigation dict.

Tests updated:
- TestQuitButtonRenders → TestClosePageShutsDownImmediately.
  Assert the shutdown caption renders + no confirm button exists.
- test_smoke EXPECTED_SUBSTRINGS["99_Close"] now pins
  "Shutting down" / "Cerrando" (the visible page body) instead of
  the removed page title.

2008 tests pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/gui/test_chrome.py

@@ -122,38 +122,33 @@ class TestLocalizedChrome:
 # Quit / Close page
 # ---------------------------------------------------------------------------
 
-class TestQuitButtonRenders:
-    """The Close page must show the localized title, body, and the
-    Close-the-app button. We don't actually click the button — that
-    would call ``os._exit(0)`` and kill the test process. We only
-    assert the button is present and its label is localized."""
+class TestClosePageShutsDownImmediately:
+    """The Close page no longer renders a confirm button — visiting the
+    page IS the close action. Under pytest the ``os._exit`` thread is
+    skipped (so the test runner doesn't suicide), but the farewell
+    success caption still renders and we assert against it."""
 
-    def test_close_page_english(self, app_factory):
+    def test_english_close_renders_shutdown_message(self, app_factory):
         app = app_factory("99_Close")
         app.run()
         text = collected_text(app)
-        assert "Close DataTools" in text
+        assert "Shutting down" in text or "Goodbye" in text, (
+            f"Close page missing shutdown caption; got:\n{text[:300]}"
+        )
+        # No confirm button — the page is the action.
         labels = [b.label for b in app.button]
-        assert any("Close the app" in lbl for lbl in labels), (
-            f"Close-the-app button missing; buttons: {labels}"
+        assert not any("Close the app" in lbl for lbl in labels), (
+            f"Close page should not render a confirm button; got: {labels}"
         )
 
-    def test_close_page_spanish(self, app_factory):
+    def test_spanish_close_renders_localized_shutdown_message(self, app_factory):
         app = app_factory("99_Close")
         with_language(app, "es")
         app.run()
         text = collected_text(app)
-        assert "Cerrar DataTools" in text
-        labels = [b.label for b in app.button]
-        assert any("Cerrar la app" in lbl for lbl in labels), (
-            f"Spanish Close button missing; buttons: {labels}"
+        # ``quit.shutting_down`` in the es pack.
+        assert "Cerrando" in text or "Apagando" in text or "Adiós" in text, (
+            f"Spanish Close page missing localized shutdown caption; got:\n{text[:300]}"
         )
 
-    def test_close_body_describes_unsaved_work_warning_es(self, app_factory):
-        app = app_factory("99_Close")
-        with_language(app, "es")
-        app.run()
-        text = collected_text(app)
-        assert "trabajo sin guardar" in text
-
 

tests/gui/test_smoke.py

@@ -61,7 +61,7 @@ EXPECTED_SUBSTRINGS: dict[str, dict[str, str]] = {
     "7_Multi_File_Merger":   {"en": "Combine Files",     "es": "Combine Files"},
     "8_Validator_Reporter":  {"en": "Quality Check",     "es": "Quality Check"},
     "9_Pipeline_Runner":     {"en": "Automated",         "es": "Automated"},
-    "99_Close":              {"en": "Close DataTools",   "es": "Cerrar DataTools"},
+    "99_Close":              {"en": "Shutting down",     "es": "Cerrando"},
 }