yoda: phase 3 — drag-drop toolbar editor in Settings

Migrates the config model from the phase-2 bag-of-bools (ToolbarItems)
to an ordered Vec<ToolbarAction> so the user can pick BOTH the set of
buttons AND their order in the toolbar.

Config (config.rs):
- new ToolbarAction enum with 11 variants (LocationUp, Reload,
  NewFolder, NewFile, Rename, Delete, Cut, Copy, Paste,
  ToggleShowHidden, OpenTerminal) + to_u8/from_u8 for DnD payload
- Config.toolbar: Vec<ToolbarAction>, default = default_toolbar()
  (NewFolder, Rename, Delete, Cut, Copy, Paste — same 6 as phase 2)

Rendering (view()):
- iterate self.config.toolbar in order and emit a tooltip'd icon button
  per entry via the new toolbar_action_ui(action) helper shared with
  the Settings page. Paste stays disabled when clipboard empty.
- No hardcoded groups or auto-dividers anymore — order is 100% user.

Settings page (toolbar_settings_section):
- two stacked lists:
  * 'Toolbar': currently-enabled actions in their Vec order. Each row
    is wrapped in dnd_source (drags a ToolbarActionPayload carrying
    the enum discriminant) + dnd_destination (accepts drops from other
    rows, fires Message::ToolbarReorder { src, target } to move src
    before target in the Vec). A list-drag-handle icon + a minus button
    (ToolbarRemove) per row.
  * 'Available': actions not yet enabled, each with a plus button
    (ToolbarAdd) that pushes to the end of the Vec.
- 'Reset to defaults' button at the bottom (ToolbarReset).

DnD infra (app.rs top):
- TOOLBAR_MIME constant: 'application/x-cosmic-files-toolbar-action'
- ToolbarActionPayload(u8) with AsMimeTypes + AllowedMimeTypes +
  TryFrom<(Vec<u8>, String)> impls — single-byte wire format matching
  the enum discriminant.

Messages:
- ToolbarAdd(ToolbarAction) — append to toolbar vec if absent
- ToolbarRemove(ToolbarAction)
- ToolbarReorder { src, target } — remove src, reinsert before target
- ToolbarReset — restore default_toolbar()

i18n (en + fr):
- new keys: toolbar-available, toolbar-empty-hint, toolbar-reset

Migration: existing installs with a phase-2 ToolbarItems struct in
their config will error at load time (different shape); cosmic_config
falls back to Self::default() which gives the phase-2 minimal-6 set —
a safe reset rather than a broken partial read.

src/config.rs

@@ -172,10 +172,11 @@ pub struct Config {
     pub show_details: bool,
     pub show_recents: bool,
     pub tab: TabConfig,
-    /// Yoda: Dolphin-style quick actions toolbar under the tab bar.
-    /// Each bool toggles one button; order in the UI is fixed (logical
-    /// grouping file-ops then clipboard then view toggles).
-    pub toolbar: ToolbarItems,
+    /// Yoda phase 3: Dolphin-style quick actions toolbar. An ordered list
+    /// of enabled buttons — position in the vec drives the toolbar order.
+    /// Reorder in Settings via drag-drop; items not in the vec are
+    /// hidden. Default = the minimal-6 set from phase 1.
+    pub toolbar: Vec<ToolbarAction>,
     pub type_to_search: TypeToSearch,
 }
 
@@ -240,46 +241,95 @@ impl Default for Config {
             show_details: false,
             show_recents: true,
             tab: TabConfig::default(),
-            toolbar: ToolbarItems::default(),
+            toolbar: default_toolbar(),
             type_to_search: TypeToSearch::Recursive,
         }
     }
 }
 
-/// Yoda: visibility toggles for each quick-action toolbar button.
-/// Default = the original "minimal 6" set (new_folder, rename, delete,
-/// cut, copy, paste). Other items default to false so users opt in.
-#[derive(Clone, Copy, CosmicConfigEntry, Debug, Deserialize, Eq, PartialEq, Serialize)]
-pub struct ToolbarItems {
-    pub new_folder: bool,
-    pub new_file: bool,
-    pub rename: bool,
-    pub delete: bool,
-    pub cut: bool,
-    pub copy: bool,
-    pub paste: bool,
-    pub reload: bool,
-    pub toggle_show_hidden: bool,
-    pub open_terminal: bool,
-    pub location_up: bool,
+/// Yoda phase 3: ordered enum of quick-action toolbar buttons.
+/// The Config stores `Vec<ToolbarAction>` so the user can pick BOTH
+/// visibility (just include/exclude the variant) AND order (position in
+/// the vec). Drag-drop reorder in the Settings page moves items around.
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, PartialEq, Serialize)]
+pub enum ToolbarAction {
+    LocationUp,
+    Reload,
+    NewFolder,
+    NewFile,
+    Rename,
+    Delete,
+    Cut,
+    Copy,
+    Paste,
+    ToggleShowHidden,
+    OpenTerminal,
 }
 
-impl Default for ToolbarItems {
-    fn default() -> Self {
-        Self {
-            new_folder: true,
-            new_file: false,
-            rename: true,
-            delete: true,
-            cut: true,
-            copy: true,
-            paste: true,
-            reload: false,
-            toggle_show_hidden: false,
-            open_terminal: false,
-            location_up: false,
+impl ToolbarAction {
+    /// Stable list of every supported action. Ordered roughly by logical
+    /// grouping (location → create/edit → clipboard → view/misc) so that
+    /// the default enabled set follows a sensible shape and the Settings
+    /// row for a not-yet-enabled action lands in a predictable spot.
+    pub const ALL: &'static [Self] = &[
+        Self::LocationUp,
+        Self::Reload,
+        Self::NewFolder,
+        Self::NewFile,
+        Self::Rename,
+        Self::Delete,
+        Self::Cut,
+        Self::Copy,
+        Self::Paste,
+        Self::ToggleShowHidden,
+        Self::OpenTerminal,
+    ];
+
+    /// u8 discriminant used to carry the action over a DnD mime payload.
+    pub const fn to_u8(self) -> u8 {
+        match self {
+            Self::LocationUp => 0,
+            Self::Reload => 1,
+            Self::NewFolder => 2,
+            Self::NewFile => 3,
+            Self::Rename => 4,
+            Self::Delete => 5,
+            Self::Cut => 6,
+            Self::Copy => 7,
+            Self::Paste => 8,
+            Self::ToggleShowHidden => 9,
+            Self::OpenTerminal => 10,
         }
     }
+
+    pub const fn from_u8(v: u8) -> Option<Self> {
+        match v {
+            0 => Some(Self::LocationUp),
+            1 => Some(Self::Reload),
+            2 => Some(Self::NewFolder),
+            3 => Some(Self::NewFile),
+            4 => Some(Self::Rename),
+            5 => Some(Self::Delete),
+            6 => Some(Self::Cut),
+            7 => Some(Self::Copy),
+            8 => Some(Self::Paste),
+            9 => Some(Self::ToggleShowHidden),
+            10 => Some(Self::OpenTerminal),
+            _ => None,
+        }
+    }
+}
+
+/// Default set shown on a fresh install — same "minimal 6" as phase 1/2.
+pub fn default_toolbar() -> Vec<ToolbarAction> {
+    vec![
+        ToolbarAction::NewFolder,
+        ToolbarAction::Rename,
+        ToolbarAction::Delete,
+        ToolbarAction::Cut,
+        ToolbarAction::Copy,
+        ToolbarAction::Paste,
+    ]
 }
 
 #[derive(Clone, Copy, Debug, Eq, Hash, PartialEq, CosmicConfigEntry, Deserialize, Serialize)]