Add cursor shape indicator for vi mode (#1558)

* feat: enable modal cursor shape in vi mode

When vi = True, users expect the cursor to reflect modal state
(block in NORMAL, beam in INSERT, underline in REPLACE).
ModalCursorShapeConfig exists in prompt_toolkit for exactly this.
Without it, cursor=None resolves to CursorShape._NEVER_CHANGE,
so no DECSCUSR sequences are ever written regardless of mode.

* Add cursor shape indicator to vi mode changelog

Author: joryeugene

changelog.rst

@@ -4,6 +4,9 @@ Upcoming (TBD)
 Features:
 ---------
 * Add support for `\\T` prompt escape sequence to display transaction status (similar to psql's `%x`).
+* Add cursor shape support for vi mode. When ``vi = True``, the terminal cursor now
+  reflects the current editing mode: beam in INSERT, block in NORMAL, underline in REPLACE.
+  Uses prompt_toolkit's ``ModalCursorShapeConfig``.
 
 4.4.0 (2025-12-24)
 ==================

pgcli/main.py

@@ -48,6 +48,7 @@
 )
 from prompt_toolkit.history import FileHistory
 from prompt_toolkit.auto_suggest import AutoSuggestFromHistory
+from prompt_toolkit.cursor_shapes import ModalCursorShapeConfig
 from pygments.lexers.sql import PostgresLexer
 
 from pgspecial.main import PGSpecial, NO_QUERY, PAGER_OFF, PAGER_LONG_OUTPUT
@@ -1087,6 +1088,7 @@ def get_continuation(width, line_number, is_soft_wrap):
                 enable_suspend=True,
                 editing_mode=EditingMode.VI if self.vi_mode else EditingMode.EMACS,
                 search_ignore_case=True,
+                cursor=ModalCursorShapeConfig(),
             )
 
             return prompt_app