Breadlock UI update: motion system, depth polish, and new animations

Adds a full motion system to the lock screen (staggered entrance, dot pop
+ caret, wrong-password shake, success flash, clock crossfade), depth
polish (gradient veil, pill shadow + hairline border, "Enter password"
hint, responsive typography), and a second wave of animations (idle
breathing, success dot cascade, status slide-in, parallax unlock drift,
animated checking ellipsis, opt-in Ken Burns wallpaper pan). Includes a
dev-only breadlock-preview harness that renders every state to PNGs with
no Wayland involved, and a design/sketch.html prototype.

Fixes text alpha being dropped by cosmic-text's glyph-mask path (all text
fades now work) and double-drifting that made the date/status overlap the
clock/pill during unlock.

breadgreet.example.toml

@@ -9,9 +9,13 @@
 mode = "color"
 path = ""
 blur = false
+# (Ken Burns is a breadlock-only background effect; not used by the greeter.)
+ken_burns = false
 
 [clock]
 format = "%H:%M"
+# strftime format for the date line under the clock; empty string hides it
+date_format = "%A · %b %d"
 
 [font]
 family = "Varela Round"