feat(knurl): add Knurl cycle texture

Knurl follows the played note and treats every cycle of the wave on its
own: a repeating level pattern over 1-16 cycles makes subharmonics in tune
with every note, random level and timing per cycle add rattle, and a noise
burst per cycle, highpassed at a multiple of f0, adds grit. Amounts are
counted in cycles, so the texture is the same on F1 and on C2.

- Cycle clock from the shared note tracker, restarted at each note; the
  audio is delayed by the lookahead plus 4.2 ms of timing-jitter headroom.
- Per-cycle randomness from a hash of the cycle number: Same every note
  or Free.
- Patterns Off, Double, Triple, Fry (default), Gallop, Stutter or drawn;
  grit switchable per step. Pattern persisted as knurl-pattern.
- Editor: last eight cycles overlaid, pattern bars with the playing step.
- Tests match the prototype: Double gives f0/2 at -8.19 dB, Triple f0/3
  at -10.68 dB, equal on F1 and C2, no added clicks, bit-exact when off,
  no allocation on the audio thread.

tools/editor-check/src/main.rs

@@ -11,11 +11,11 @@ fn main() {
         .map(|a| a[1].as_str())
         .unwrap_or("rivet");
     if ![
-        "rivet", "patina", "anvil", "crucible", "lathe", "temper", "weld",
+        "rivet", "patina", "anvil", "crucible", "lathe", "temper", "weld", "knurl",
     ]
     .contains(&plugin)
     {
-        eprintln!("Use --plugin rivet, patina, anvil, crucible, lathe, temper or weld");
+        eprintln!("Use --plugin rivet, patina, anvil, crucible, lathe, temper, weld or knurl");
         std::process::exit(2);
     }
     let patina = plugin == "patina" || args.iter().any(|arg| arg == "--resonance");
@@ -25,7 +25,10 @@ fn main() {
     let lathe = plugin == "lathe";
     let temper = plugin == "temper";
     let weld = plugin == "weld";
-    let (width, height) = if weld {
+    let knurl = plugin == "knurl";
+    let (width, height) = if knurl {
+        (knurl_ui::WIDTH, knurl_ui::HEIGHT)
+    } else if weld {
         (weld_ui::WIDTH, weld_ui::HEIGHT)
     } else if temper {
         (temper_ui::WIDTH, temper_ui::HEIGHT)
@@ -146,6 +149,22 @@ fn main() {
         }
         temper_state.accept_frame(engine.take_analyzer());
     }
+    let mut knurl_settings = knurl_core::Settings::default();
+    let mut knurl_state = knurl_ui::State::default();
+    if knurl {
+        // An F1 saw bass with the default Fry pattern, jitter and grit.
+        let mut engine = knurl_core::Engine::new(48000., 2).unwrap();
+        engine.set_settings(knurl_settings).unwrap();
+        let mut saw = common_dsp::Saw::new(48000., 43.65);
+        for i in 0..36000 {
+            let x = (saw.sample() * 2.2).tanh() * 0.5;
+            engine.process_sample([x, x]);
+            if i % 1600 == 0 {
+                knurl_state.accept_frame(engine.take_analyzer());
+            }
+        }
+        knurl_state.accept_frame(engine.take_analyzer());
+    }
     let mut weld_settings = weld_core::Settings::default();
     let mut weld_state = weld_ui::State::default();
     if weld {
@@ -275,7 +294,9 @@ fn main() {
     let session_motif = session.motifs[0].id;
     shared.replace(session).unwrap();
     let ctx = egui::Context::default();
-    if weld {
+    if knurl {
+        knurl_ui::style(&ctx);
+    } else if weld {
         weld_ui::style(&ctx);
     } else if temper {
         temper_ui::style(&ctx);
@@ -310,7 +331,9 @@ fn main() {
             },
             |ui| {
                 egui::CentralPanel::default().show(ui, |ui| {
-                    if weld {
+                    if knurl {
+                        knurl_ui::show(ui, &mut knurl_settings, &mut knurl_state);
+                    } else if weld {
                         weld_ui::show(ui, &mut weld_settings, &mut weld_state);
                     } else if temper {
                         temper_ui::show(ui, &mut temper_settings, &mut temper_state);