fix(editor): guard flex children on drag + property-panel and desktop chrome fixes

Canvas / layout:
- Guard flex flow-children from free-drag and add a 4px drag threshold,
  so a first click no longer materializes x/y on a flow child and
  collapses the auto-layout frame.

Property panel:
- Gap/justify radios disable the gap input on space-between/around;
  compact gap rows with vertically-centered input text.
- Padding-mode gear popover hover; the pin is anchor-scoped so it no
  longer leaks into the next selection.
- Font-weight dropdown: full 100-900 numeric options + row hover.
- Stroke hex seeds the displayed swatch colour (not #000000); stroke
  width now persists on commit.

Desktop:
- Traffic-light inset now applies on launch (casement windowDidBecomeKey).
- File-drop overlay; git commit caret blink.

Refactor:
- Split property_dispatch / git_panel / property-panel tests under the
  800-line cap; reorganise panel tests by topic.

crates/op-editor-core/src/agent_settings.rs

@@ -439,6 +439,7 @@ impl AgentSettings {
         )
     }
 
+    #[allow(clippy::too_many_arguments)]
     pub fn add_acp_agent_config(
         &mut self,
         display_name: impl Into<String>,

crates/op-editor-core/src/test_support.rs

@@ -169,6 +169,7 @@ pub fn flex_frame(
             ..Default::default()
         },
         children: Some(children),
+        image_search_query: None,
         reusable: None,
         slot: None,
         state: None,