Dock: move app-side dock code into app::dock, trim tests, drop icon tooltip

- The dock's state handling and drawing move out of update/dialog.rs and
  view/mod.rs into src/app/dock/ (update.rs, view.rs, tests.rs). The
  overlay view_main stacked over the workspace (floating pallets, + menu,
  drag preview, pointer capture) becomes one `dock_overlay` call. Code is
  moved, not changed.
- Strip icons no longer show the pallet name on hover.
- Tests trimmed where they overlapped: the top / bottom half drops are
  one test, the two hover tests are one, and the in-group icon reorder,
  raise-float, empty floating title bar and slot-span tests are dropped
  (each is covered by another test).

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

src/app/dock/mod.rs

@@ -0,0 +1,12 @@
+//! The app side of docking: pallets docked on the drawing view's edges (one
+//! group shown per edge, listed in an icon strip) or floating over it.
+//!
+//! The persisted layout and its pure geometry live in [`crate::ui::dock`];
+//! this module holds the transient state handling (`update`) and drawing
+//! (`view`).
+
+mod update;
+mod view;
+
+#[cfg(test)]
+mod tests;