Add the library, collections, and trash views; theme from style.yaml

The UI gains the views the catalog work was building toward: a windowed
library grid with ratings and flags, the collection tree with drag-to-add,
and trash with restore. derived_sync pushes thumbnail shards and the catalog
snapshot to the server's derived folder.

Tokens now have one source of truth. build.rs reads style.yaml and generates
theme.slint into OUT_DIR, which answers every existing
`import { Theme } from "theme.slint"` unchanged, because Slint resolves
imports against the importing file's directory first and the include paths
after. Generating into OUT_DIR rather than beside the hand-written Slint is
the point: a generated file sitting in ui/ looks exactly like the files
around it that are meant to be edited, and an edit to it would survive until
the next touch of style.yaml — a bug that hides for weeks. build.rs fails
loudly if a stale ui/theme.slint exists, which would otherwise shadow the
generated one silently and make every palette change vanish with no error.

The palette moves to near-neutral dark with achromatic signalling, so the
accent means "modified" or "active" rather than "heading". Shared components
land in widgets.slint: a token that binds several values into one concept is
a component, not a row in a YAML file.

Adds an optional live-style feature that makes the tokens in-out so they can
be written at startup — a feature rather than the default because it stops
the properties being constant-folded.

serde_norway is the YAML crate: serde_yaml and serde_yml are both deprecated,
and its mappings preserve insertion order, which is what lets the generated
Slint keep the token ordering the author chose.

Assisted-by: LLM

ui/dr-ui/src/launch.rs

@@ -29,6 +29,23 @@ pub enum LaunchState {
     },
 }
 
+/// What the app opens on.
+///
+/// Three outcomes, and the middle one is easy to lose: a configured library
+/// means the launch screen is skipped, and skipping it must not also skip
+/// opening the library — otherwise the app lands on an empty view with no
+/// route back to the grid, because the "Open library" button is on the screen
+/// that was never shown.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Startup {
+    /// Files were named on the command line; show those.
+    ShowLocalFiles,
+    /// An account and a folder are configured; scan and show the grid.
+    OpenLibrary,
+    /// Nothing configured; ask the user to sign in.
+    ShowLaunchScreen,
+}
+
 /// TRACES: FR-NC-1 | FR-NC-4 | M-1 | M-3 | M-4
 /// Everything the launch screen renders from.
 #[derive(Debug, Clone)]
@@ -197,6 +214,23 @@ impl LaunchModel {
         self.is_signed_in() && !self.library_root().is_empty()
     }
 
+    /// What the app should do on startup.
+    ///
+    /// Pure so it can be tested without a secret store or a display server —
+    /// and it needs testing, because the interesting case is the one with no
+    /// visible symptom until you are staring at an empty window.
+    pub fn startup_action(&self, have_local_paths: bool) -> Startup {
+        if have_local_paths {
+            // Files named on the command line win: the user asked for those
+            // specifically, not for their library.
+            Startup::ShowLocalFiles
+        } else if self.can_open_library() {
+            Startup::OpenLibrary
+        } else {
+            Startup::ShowLaunchScreen
+        }
+    }
+
     pub fn format_filter(&self) -> FormatFilter {
         FormatFilter::from_formats(self.formats.iter().filter(|(_, on)| *on).map(|(f, _)| *f))
     }
@@ -393,6 +427,38 @@ mod tests {
         assert!(m.can_open_library());
     }
 
+    #[test]
+    fn a_configured_library_opens_rather_than_showing_nothing() {
+        // The regression this guards: skipping the launch screen because a
+        // library is configured used to mean the library was never opened,
+        // since `on_open_library` only fires from a button nobody saw.
+        let mut m = LaunchModel::default();
+        m.signed_in(session_with_root("PhotosRaw"));
+        assert_eq!(m.startup_action(false), Startup::OpenLibrary);
+    }
+
+    #[test]
+    fn no_configuration_shows_the_launch_screen() {
+        let m = LaunchModel::default();
+        assert_eq!(m.startup_action(false), Startup::ShowLaunchScreen);
+    }
+
+    #[test]
+    fn a_signed_in_account_without_a_folder_still_needs_the_screen() {
+        // Opening without a chosen folder would scan the whole account.
+        let mut m = LaunchModel::default();
+        m.signed_in(session_with_root(""));
+        assert_eq!(m.startup_action(false), Startup::ShowLaunchScreen);
+    }
+
+    #[test]
+    fn command_line_files_win_over_a_configured_library() {
+        // The user asked for those files specifically.
+        let mut m = LaunchModel::default();
+        m.signed_in(session_with_root("PhotosRaw"));
+        assert_eq!(m.startup_action(true), Startup::ShowLocalFiles);
+    }
+
     #[test]
     fn a_failure_never_strands_the_screen_in_busy() {
         let mut m = LaunchModel::default();