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/node_graph.rs

@@ -584,7 +584,7 @@ impl Graph {
     /// The node library as a docked panel: title bar, a search box with the
     /// graph's New / Open / Save beside it, then the categories. Entries are
     /// clicked or dragged onto the canvas.
-    pub fn panel(&self, width: f32, auto_collapse: bool) -> Element<'_, Message> {
+    pub fn panel(&self, width: f32, chrome: crate::ui::dock::Chrome) -> Element<'_, Message> {
         use crate::ui::dock::{self, PanelId};
         let tool = |icon: &'static [u8], tip: &str, message: GraphMsg| {
             dock::tool_button(
@@ -663,12 +663,8 @@ impl Graph {
         .height(Length::Fill);
 
         dock::frame(
-            column![
-                dock::title_bar(PanelId::NodeGraph, t!("Node Graph").into_owned(), auto_collapse),
-                toolbar,
-                body
-            ]
-            .spacing(6),
+            dock::title_bar(PanelId::NodeGraph, t!("Node Graph").into_owned(), chrome),
+            column![toolbar, body].spacing(6),
             width,
         )
     }