refactor(gui_2): merge command_palette; split registry->commands + render->gui_2; git rm src/command_palette.py

Per spec FR1 + Phase 1.3 + architecture feedback: src/command_palette.py
split by responsibility:
  - Command/ScoredCommand/CommandRegistry/fuzzy_match/_close_palette/_execute (data/ops)
    -> src/commands.py (which already owns _LazyCommandRegistry pattern)
  - render_palette_modal (view/ImGui) -> src/gui_2.py

GUI is a pure view; the registry/data classes are ops; commands.py owns
the registry because commands.py is where @registry.register decorators live.
gui_2.render_palette_modal imports Command from commands.py to type its
parameters.

Also fixes Phase 1.1 (bg_shader) per architecture feedback:
BackgroundShader no longer owns 'enabled' state - the GUI is pure view.
State is now owned by AppController.bg_shader_enabled (read on load from
config, written from gui_2 checkbox via app's __setattr__ delegation).

Tests:
- tests/test_command_palette.py: imports from src.commands (was src.command_palette)
- tests/test_commands_no_top_level_command_palette.py: rewritten for the
  new architecture (eager registry in commands.py; render in gui_2; no
  circular import between commands.py and gui_2)

src/gui_2.py

@@ -24,7 +24,8 @@ if _thirdparty not in sys.path:
 
 from contextlib   import ExitStack, nullcontext
 from pathlib      import Path
-from typing       import Optional, Any
+from typing       import Optional, Any, Callable, Dict, List
+from dataclasses  import dataclass, field
 from imgui_bundle import imgui, hello_imgui, immapp, imgui_node_editor as ed, imgui_color_text_edit as ced
 
 # Lazy proxies (startup_speedup_20260606 Phase 5D)
@@ -1093,9 +1094,9 @@ class App:
   pushed_prior_tint = False
   
   # Render background shader
-  bg = get_bg()
-  ws = imgui.get_io().display_size
-  if bg.enabled: bg.render(ws.x, ws.y)
+  if getattr(self, 'bg_shader_enabled', False):
+   ws = imgui.get_io().display_size
+   get_bg().render(ws.x, ws.y)
 
   theme.render_post_fx(ws.x, ws.y, self.ai_status, self.ui_crt_filter)
   
@@ -6265,13 +6266,14 @@ def render_theme_panel(app: App) -> None:
   ch_ct, ctrans = imgui.slider_float("##ctrans", theme.get_child_transparency(), 0.1, 1.0, "%.2f")
   if ch_ct:
    theme.set_child_transparency(ctrans)
-  bg                = get_bg()
-  ch_bg, bg.enabled = imgui.checkbox("Animated Background Shader", bg.enabled)
-  if ch_bg:
+  bg_enabled       = getattr(self, 'bg_shader_enabled', False)
+  ch_bg, new_bg    = imgui.checkbox("Animated Background Shader", bg_enabled)
+  if ch_bg and new_bg != bg_enabled:
+   self.bg_shader_enabled = new_bg
    gui_cfg = app.config.setdefault("gui", {})
-   gui_cfg["bg_shader_enabled"] = bg.enabled
-   app._flush_to_config()
-   app.save_config()
+   gui_cfg["bg_shader_enabled"] = new_bg
+   if hasattr(app, "_flush_to_config"): app._flush_to_config()
+   if hasattr(app, "save_config"):     app.save_config()
 
   ch_crt, app.ui_crt_filter = imgui.checkbox("CRT Filter", app.ui_crt_filter)
   if ch_crt:
@@ -8443,12 +8445,11 @@ _bg: _Optional["BackgroundShader"] = None
 
 class BackgroundShader:
  def __init__(self):
-  self.enabled = False
   self.start_time = _bg_time.time()
   self.ctx: _Optional[_Any] = None
 
  def render(self, width: float, height: float):
-  if not self.enabled or width <= 0 or height <= 0:
+  if width <= 0 or height <= 0:
    return
   t = _bg_time.time() - self.start_time
   dl = imgui.get_background_draw_list()
@@ -8506,3 +8507,59 @@ def draw_soft_shadow(draw_list: imgui.ImDrawList, p_min: imgui.ImVec2, p_max: im
    thickness=1.0
   )
 #endregion: Shaders
+
+#region: Command Palette Modal (rendering only; registry lives in src/commands.py)
+from src.commands import Command as _CpCommand, fuzzy_match as _cp_fuzzy_match, _close_palette, _execute as _cp_execute
+
+def render_palette_modal(app: Any, commands: List[Any]) -> None:
+ if not getattr(app, "show_command_palette", False):
+  return
+ viewport = imgui.get_main_viewport()
+ center   = viewport.get_center()
+ imgui.set_next_window_pos((center.x - 300, center.y - 200), imgui.Cond_.always)
+ imgui.set_next_window_size((600, 400), imgui.Cond_.always)
+ if not hasattr(app, "_command_palette_query"):    app._command_palette_query    = ""
+ if not hasattr(app, "_command_palette_selected"): app._command_palette_selected = 0
+ if not hasattr(app, "_command_palette_focused"):  app._command_palette_focused  = False
+ if not app._command_palette_focused:
+  imgui.set_next_window_focus()
+  app._command_palette_focused = True
+ if imgui.is_key_pressed(imgui.Key.escape):
+  _close_palette(app)
+  return
+ expanded, opened = imgui.begin("Command Palette##manual_slop", True, imgui.WindowFlags_.no_collapse)
+ if not expanded or not opened:
+  app.show_command_palette     = False
+  app._command_palette_focused = False
+  imgui.end()
+  return
+ if not getattr(app, '_command_palette_input_focused', False):
+  imgui.set_keyboard_focus_here()
+  app._command_palette_input_focused = True
+ results = _cp_fuzzy_match(app._command_palette_query, commands, top_n=20)
+ if results: app._command_palette_selected = max(0, min(app._command_palette_selected, len(results) - 1))
+ else:       app._command_palette_selected = 0
+ if imgui.is_key_pressed(imgui.Key.down_arrow):
+  if results:
+   app._command_palette_selected = min(app._command_palette_selected + 1, len(results) - 1)
+ if imgui.is_key_pressed(imgui.Key.up_arrow):
+  if results:
+   app._command_palette_selected = max(app._command_palette_selected - 1, 0)
+ if imgui.is_key_pressed(imgui.Key.enter) or imgui.is_key_pressed(imgui.Key.keypad_enter):
+  if results and 0 <= app._command_palette_selected < len(results):
+   _cp_execute(app, results[app._command_palette_selected].command)
+ imgui.set_next_item_width(-1)
+ _, app._command_palette_query = imgui.input_text("##query", app._command_palette_query)
+ if imgui.begin_child("##results", (0, -1)):
+  for i, scored in enumerate(results):
+   is_selected = (i == app._command_palette_selected)
+   label      = f"[{scored.command.category}] {scored.command.title}"
+   clicked, _ = imgui.selectable(label, is_selected)
+   if clicked:
+    app._command_palette_selected = i
+    _cp_execute(app, scored.command)
+  if not results:
+   imgui.text_disabled("No matching commands.")
+ imgui.end_child()
+ imgui.end()
+#endregion: Command Palette Modal