Dock: flush title bars and a vertical title bar for floating panels

Every docked panel now shows its title bar flush along the top, like the
Properties panel: dock::frame takes the title bar separately and pads
only the content below it.

A floating panel drops its horizontal title bar for a vertical one on
the side facing the nearer workspace edge. Close and the auto-hide pin
sit at the top; the panel's icon sits at the bottom with the title
reading upward above it. The free part of the bar drags the panel. With
auto-hide on, a floating panel shrinks to its title bar until hovered.

Panel views take a dock::Chrome (auto-collapse plus floating) in place
of the bare auto-collapse flag, so the shared title bar knows when to
step aside.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013RyGiMXcsf9HTKfqDxaQGt

src/ui/properties.rs

@@ -542,11 +542,11 @@ impl PropertiesPanel {
             .unwrap_or_default()
     }
 
-    pub fn view(&self, width: f32, auto_collapse: bool) -> Element<'_, Message> {
+    pub fn view(&self, width: f32, chrome: crate::ui::dock::Chrome) -> Element<'_, Message> {
         use crate::ui::dock::PanelId;
         // ── Header ──────────────────────────────────────────────────────────
         let header =
-            crate::ui::dock::title_bar(PanelId::Properties, t!("Properties").into_owned(), auto_collapse);
+            crate::ui::dock::title_bar(PanelId::Properties, t!("Properties").into_owned(), chrome);
 
         // ── Title bar (entity type / "No Selection") ─────────────────────
         let title_content: Element<'_, Message> = if self.selection_groups.is_empty() {