test(home): move marker to true bottom of main content

User reported the previous TEST #2 banner appeared at the *top* of
the main content area instead of the bottom. Root cause: on the home
page, ``render_sticky_footer()`` is called at line 107 — before
``st.title()`` — so anything that function injects in document flow
lands at the top of ``stAppViewBlockContainer``. Other pages call
``render_sticky_footer()`` at the end of their script, so the flow
content lands at the bottom there.

Remove the marker from ``render_sticky_footer`` and add it directly
at the very end of ``_home._home_page()`` — after the findings
panels. If this banner lines up with the offending white strip when
scrolled to the bottom, the strip is something rendered at the tail
of the page (likely an iframe wrapper from ``render_findings_panel``
or the block container's ``padding-bottom``).

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

src/gui/_home.py

@@ -288,3 +288,17 @@ def _home_page() -> None:
                         header=f"📄 {name}",
                         key_namespace=name,
                     )
+
+    # TEMP: visible marker at the very end of the home page's main
+    # content. Used to locate the "white bar" the user wants removed.
+    # If this red banner lines up with the offending white strip when
+    # scrolled to the bottom, the strip is something rendered right
+    # here at the tail of ``stAppViewBlockContainer``.
+    st.markdown(
+        '<div style="background:#ffe0e0;border:2px dashed #b00020;'
+        'color:#b00020;font-weight:700;font-size:13px;text-align:center;'
+        'padding:8px 12px;margin:4px 0;font-family:system-ui,sans-serif;">'
+        '◀ CLAUDE TEST #3 — END OF MAIN CONTENT — IS THIS THE WHITE BAR? ▶'
+        '</div>',
+        unsafe_allow_html=True,
+    )