shell: add spotlight builtin (theme 04), dots/placeholder-clock schema, and anim::spring_to

- bread-theme:🐚 WorkspacesModule.dot_widths and ClockModule.placeholder_clock,
  resolved/validated in manifest.rs and modeled in types.rs, so a theme can
  actually configure dot-pill widths and an entry-as-clock placeholder
  instead of those staying schema-only.
- New compiled-in builtin "spotlight" (assets/shell/spotlight/), registered
  in builtin.rs so list() returns three themes: centred capsule window spec
  (anchors=[top] only, width=480, exclusive=none, keyboard=on_demand),
  workspaces.style=dots, clock.style=none+placeholder_clock, launcher.mode=
  embedded, drawer=[launcher_results]. Colours are palette token names
  (pink), never hex.
- bread-theme::anim::spring_to: a reusable TickCallback size-interpolation
  helper (GTK4 has no CSS width/height transition on a widget or layer-shell
  surface), generalized from WorkspaceTrail's existing ease/tick pattern, for
  breadbar's capsule-drawer expand/collapse.
- bread_launcher::LAUNCHER_APP: the launcher's one shared on-disk identity
  (cache/config/history), so breadbar's embedded capsule and breadbox's
  overlay window read and write the SAME cache and launch history rather
  than forking into two rankings of a user's apps.

Tests: +6 spotlight builtin tests (loads/in list/capsule window shape/
embedded mode/dots widths/flat-pink-not-hex), bread-theme --lib 63->69,
bread-launcher --lib unchanged at 18.

bread-theme/src/lib.rs

@@ -1,6 +1,8 @@
 #[cfg(feature = "adw")]
 pub mod adw;
 #[cfg(feature = "gtk")]
+pub mod anim;
+#[cfg(feature = "gtk")]
 pub mod gtk;
 mod layerrules;
 mod output;