Use analytic springs and instrument resize barriers

Share a stable damped oscillator solver across scalar and rectangle animations while preserving retarget and explicit no-crossing presentation policies. Add deterministic traces, scrolling and zoom continuity coverage, and pause-aware advancement.

Measure resize barrier and handoff timing behind resize-metrics, expose the feature through the release installer, and wait for the intended backend in isolated portal tests.

compositor/src/state/outputs.rs

@@ -2,6 +2,10 @@ use super::*;
 
 impl Ferese {
     pub fn register_output(&mut self, output: &Output, identity: String) {
+        if self.output_ids.is_empty() {
+            self.reset_animation_clock();
+        }
+
         if self.session_lock.active {
             self.session_lock.output_added(output);
             self.lock_input_activity();