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.

docs/installation.md

@@ -244,6 +244,7 @@ Installer options:
 ```sh
 ./scripts/install.sh --dry-run
 ./scripts/install.sh --offline --release-id my-build
+./scripts/install.sh --resize-metrics
 ./scripts/install.sh --skip-build
 ```
 
@@ -252,6 +253,10 @@ cached, or `--skip-build` after building every component from the revision you w
 install. The latter uses binaries already in `target/release/`, and
 `./scripts/install.sh --help` lists all available options.
 
+Use `--resize-metrics` to enable resize-barrier counters and duration histograms in
+the release build. Ferese prints the measurements to its session log on normal exit.
+This option requires building and cannot be combined with `--skip-build`.
+
 ## Logout and recovery
 
 Save your work before leaving: **Super+Shift+E** and `feresectl request-logout` ask for