refactor: run Lathe, Temper and Knurl as tracked modules

Add a Tracked trait and a Lookahead harness to common-dsp. Each engine is
now its tracker plus a module that follows note events aligned with its
input, so the same module can run behind a shared tracker.

Lathe and Temper output is bit-exact against the old engines. Knurl's
interpolation now reads one newer sample inside the module, so its
latency is one sample longer; the output matches within float rounding.

Each editor exposes body() and toggles() besides show(), so another
editor can draw a module's page.

plugins/temper/ui/src/lib.rs

@@ -233,14 +233,7 @@ pub fn show(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
         if r.clicked() {
             settings.bypass = !settings.bypass;
         }
-        let r = ui
-            .selectable_label(settings.auto_gain, RichText::new("AUTO GAIN").size(13.))
-            .on_hover_text(
-                "Match output loudness to the input, so Drive changes character, not level.",
-            );
-        if r.clicked() {
-            settings.auto_gain = !settings.auto_gain;
-        }
+        toggles(ui, settings);
         ui.separator();
         for (source, label) in [(Source::Midi, "MIDI"), (Source::Audio, "AUDIO")] {
             let r = ui.selectable_label(settings.source == source, RichText::new(label).size(13.));
@@ -250,6 +243,13 @@ pub fn show(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
         }
         caption(ui, "PITCH FROM");
     });
+    body(ui, settings, state);
+    ui.separator();
+    ui.label(RichText::new(&state.help).color(MUTED));
+}
+
+/// Everything under the header: the standalone editor and Forge both draw it.
+pub fn body(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
     ui.add_space(6.);
     let frame = state.analyzer;
     ui.horizontal_top(|ui| {
@@ -294,8 +294,6 @@ pub fn show(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
         ui.set_width(ui.available_width());
         ui.vertical(|ui| controls(ui, settings, state));
     });
-    ui.separator();
-    ui.label(RichText::new(&state.help).color(MUTED));
 }
 const TOP: f32 = 290.;
 
@@ -411,3 +409,15 @@ fn controls(ui: &mut egui::Ui, settings: &mut Settings, state: &mut State) {
             "Output trim.");
     });
 }
+
+/// Header switches besides Bypass and the pitch source.
+pub fn toggles(ui: &mut egui::Ui, settings: &mut Settings) {
+    let r = ui
+        .selectable_label(settings.auto_gain, RichText::new("AUTO GAIN").size(13.))
+        .on_hover_text(
+            "Match output loudness to the input, so Drive changes character, not level.",
+        );
+    if r.clicked() {
+        settings.auto_gain = !settings.auto_gain;
+    }
+}