Context/desktop menu polish: real hover tint, real separator line, Select All

Reported live: "looks weird and unpolished... need a lot more items".
Compared directly against the exact AGS reference this project's own
menu rebuild already targets rather than guessing:

- Highlighted rows used a flat, fully-saturated fill instead of the
  reference's subtle 22%-accent-into-background wash. New decoration::
  color::mix_rgb (channel-wise linear blend, generalizing brighten/
  darken's fixed-target blends to an arbitrary second colour/ratio) lets
  render_context_menu reproduce that same ratio.
- Every separator row was a label string of Unicode box-drawing
  characters rendered as text glyphs, which render inconsistently at
  small sizes - a label that's entirely U+2500 now draws a real 1px
  hairline instead; a label that mixes it with real text ("--- Move to
  Workspace ---", a deliberate section-header convention) still renders
  as text, unchanged.
- "Select All" added to the bare-desktop menu, the one action every
  mainstream desktop's own menu offers that this one lacked.

New tests needed real care: the panel's own rounded-corner distance
field softens alpha within its radius of any canvas edge, not just the
visible corners, so a naive full-row pixel scan against bg picked that
up as a false positive on the first attempt - fixed by scanning only
rows/columns confirmed (via a throwaway debug dump) to sit inside the
panel's genuinely flat interior.

Full workspace build/test/clippy clean, built and installed. Real
submenus and per-row icons remain real, separate scope - this
project's floating-menu UI has no nested-panel concept yet.

1 files changed, 19 insertions, 0 deletions

diff --git a/crates/wayland/src/state/desktop_icons.rs b/crates/wayland/src/state/desktop_icons.rs
index 81a8ed8..a1b1968 100644
--- a/crates/wayland/src/state/desktop_icons.rs
+++ b/crates/wayland/src/state/desktop_icons.rs
@@ -218,6 +218,24 @@ impl CompState {
         }
     }
 
+    /// Selects every desktop icon at once - the bare-desktop menu's own
+    /// "Select All" action (see `DesktopMenuAction::SelectAll`'s own doc
+    /// comment). Same "only rebuild the buffers that actually changed"
+    /// shape as `select_desktop_icon`.
+    pub(crate) fn select_all_desktop_icons(&mut self) {
+        let Some(icons) = &mut self.desktop_icons else { return };
+        let mut changed = Vec::new();
+        for icon in &mut icons.icons {
+            if !icon.selected {
+                icon.selected = true;
+                changed.push(icon.id.clone());
+            }
+        }
+        for id in changed {
+            self.rebuild_icon_buffer(&id);
+        }
+    }
+
     /// Starts a rubber-band selection at `pos` (global space) - clears
     /// whatever was selected before, matching real desktop convention
     /// (Windows/GNOME/macOS all start a fresh marquee selection, not an
@@ -603,6 +621,7 @@ impl CompState {
             DesktopMenuAction::NewTextFile => self.new_desktop_text_file(),
             DesktopMenuAction::OpenTerminalHere => self.open_terminal_here(),
             DesktopMenuAction::OpenInFileManager => self.open_desktop_in_file_manager(),
+            DesktopMenuAction::SelectAll => self.select_all_desktop_icons(),
             DesktopMenuAction::Refresh => self.refresh_desktop_icons(),
             // Never actually reached - the click-dispatch site intercepts
             // `Separator` first, same as `context_menu::MenuAction::