fix(tui): refresh shell-mode footer budget and strengthen resize assertion

Shell-mode rendering never set _prompt_footer_row_budget, so
_fit_toolbar_to_terminal clipped the bottom toolbar against a stale
agent-mode value (or the initial 0, hiding the footer entirely in a
pure shell session). Refresh it every shell render. Replace a
trivially-true pyte row-count assertion in the resize e2e with a
width-overflow check.

Author: elkaix

src/pythinker_code/ui/shell/prompt.py

@@ -3127,6 +3127,11 @@ def _render_message(self) -> FormattedText:
     def _render_shell_prompt_message(self) -> FormattedText:
         frame = self._prompt_frame_for_render()
         columns = frame.columns
+        # Shell mode has no running-prompt scene allocator, so the footer keeps
+        # its natural height within the terminal. Refresh the budget every render
+        # (not just on the agent path) so a mode switch or resize cannot leave
+        # _fit_toolbar_to_terminal clipping against a stale agent-mode value.
+        self._prompt_footer_row_budget = frame.terminal_rows
         fragments: FormattedText = FormattedText()
 
         if getattr(self, "_shortcut_help_open", False):

tests/e2e/test_shell_pty_prompt_layout_e2e.py

@@ -269,8 +269,11 @@ def test_prompt_scene_survives_shrinking_terminal_heights(tmp_path: Path) -> Non
             assert shell.process.poll() is None, f"shell died after resize to {height} rows"
             post_resize = shell._raw_chunks[resize_chunk_start:]
             if post_resize:
+                # pyte always yields exactly `height` lines, so assert observable
+                # behavior instead: the redraw never wraps a row past the terminal
+                # width and never fossilizes an input-card border above content.
                 rows = _render_sized(post_resize, _COLS, height)
-                assert len(rows) == height
+                assert all(len(row) <= _COLS for row in rows)
                 assert not _has_fossil_border_above_content(rows)
 
         _set_window_size(shell.master_fd, columns=_COLS, lines=_ROWS)