refactor: remove split_pane_manager plugin and harden view handling

- Delete deprecated split_pane_manager command plugin and all related commands
- Introduce new split_pane command structure (untracked replacement)
- Add guard in code_minimap to handle missing active view
- Prevent language detection for non-file buffers in command_helpers

This cleans up legacy split pane logic and improves stability for edge cases.

plugins/code/commands/split_pane/close_split_view.py

@@ -0,0 +1,77 @@
+# Python imports
+
+# Lib imports
+import gi
+
+gi.require_version('Gtk', '3.0')
+gi.require_version('GtkSource', '4')
+
+from gi.repository import Gtk
+from gi.repository import GtkSource
+
+# Application imports
+from libs.event_factory import Event_Factory, Code_Event_Types
+
+
+
+emit_to: callable = None
+
+def get_source_view(widget):
+    if isinstance(widget, GtkSource.View):
+        return widget
+
+    if isinstance(widget, Gtk.ScrolledWindow):
+        return widget.get_child()
+
+    if isinstance(widget, Gtk.Paned):
+        return get_source_view(widget.get_child1())
+
+    return None
+
+
+def execute(
+    source_view,
+    char_str,
+    modkeys_states
+):
+    logger.debug("Command: Close Split Pane")
+
+    scrolled_win = source_view.get_parent()
+    pane         = scrolled_win.get_parent()
+
+    if not isinstance(pane, Gtk.Paned): return
+
+    container    = pane.get_parent()
+    source_view1 = pane.get_child1()
+    source_view2 = pane.get_child2()
+
+    if scrolled_win == source_view1:
+        remaining    = source_view2
+        closing_view = source_view
+    else:
+        remaining    = source_view1
+        closing_view = source_view
+
+    remaining_view = get_source_view(remaining)
+    left           = closing_view.sibling_left
+    right          = closing_view.sibling_right
+
+    if left:
+        left.sibling_right = right
+
+    if right:
+        right.sibling_left = left
+
+    pane.remove(source_view1)
+    pane.remove(source_view2)
+
+    container.remove(pane)
+    container.add(remaining)
+
+    event = Event_Factory.create_event(
+        "remove_source_view",
+        view = closing_view
+    )
+    emit_to("source_views", event)
+
+    remaining_view.grab_focus()