feat: stable note tracking, NOTE pitch source and unsure fallback

Producers found the tracked plugins jumpy: the shared tracker switched notes
after 10 ms and retuned every 5 ms, so growls and formant basses flickered
and every tracked plugin acted on wrong notes.

Shared tracker (common-dsp):
- A new note needs a steady read for 40 ms; an octave down 80 ms, an octave
  up 200 ms (an octave-up read still fits the note's period and counts as
  agreeing). Inside a note the tuning only moves past a 0.25 semitone
  deadband. Follow bends keeps the old fast behaviour as an option.
- A trust score turns the note unsure while reads disagree; Tracker::active
  and NoteState report it, and Fallback latches "step back" across note ends.
- Notes end when the window start stays below the gate's release level for
  20 ms, so short gaps between notes are seen without waiting for the gate.
- PitchSource replaces the old (midi, gate, glide) arguments: Audio, MIDI or
  Note mode (a set note, no detection), plus a key lock (minor, major, root
  only) that snaps reads to the key.
- stems.rs: synthetic stems (growls, wobble, reese, formant, 808 slide,
  layered drop, noise riser) and a score; examples/tracker_report scores the
  corpus or real WAV stems. On the corpus the old behaviour makes up to 28
  extra note starts per second; the stable default makes none.

Plugins:
- Anvil, Lathe, Temper, Knurl, Planish, Braze and Forge gain the NOTE pitch
  source, the key lock and Follow bends (shared common-params crate and a
  shared header switch in common-ui).
- Unsure tracking: Anvil brings the original sub back in place of the sine,
  Lathe passes the audio through, Knurl fades its texture out; Temper,
  Planish and Braze hold their last sure tuning. Readouts show the note only
  when it is sure.
- Anvil gains Mode: Replace or Enhance (keeps the original sub and adds the
  sine under it).
- Planish slides its band edges over 6 ms on a new note instead of snapping.
- Ballast defaults to Grid parts, which need no tracking.

plugins/forge/plugin/Cargo.lock

@@ -309,11 +309,23 @@ dependencies = [
 [[package]]
 name = "common-dsp"
 version = "0.1.0"
+dependencies = [
+ "serde",
+]
+
+[[package]]
+name = "common-params"
+version = "0.1.0"
+dependencies = [
+ "common-dsp",
+ "nih_plug",
+]
 
 [[package]]
 name = "common-ui"
 version = "0.1.0"
 dependencies = [
+ "common-dsp",
  "egui",
 ]
 
@@ -646,6 +658,7 @@ name = "forge"
 version = "0.1.0"
 dependencies = [
  "clap-sys",
+ "common-params",
  "crossbeam-queue",
  "forge-core",
  "forge-ui",

plugins/forge/plugin/Cargo.toml

@@ -13,6 +13,7 @@ crate-type = ["cdylib", "rlib"]
 nih_plug = { git = "https://github.com/robbert-vdh/nih-plug.git", rev = "de421011f41a6d10fc8c7a6084e4f4dee0143683", default-features = false }
 nih_plug_egui = { git = "https://github.com/robbert-vdh/nih-plug.git", rev = "de421011f41a6d10fc8c7a6084e4f4dee0143683" }
 forge-core = { path = "../core" }
+common-params = { path = "../../common/params" }
 lathe-core = { path = "../../lathe/core" }
 temper-core = { path = "../../temper/core" }
 knurl-core = { path = "../../knurl/core" }

plugins/forge/plugin/src/params.rs

@@ -1,3 +1,4 @@
+use common_params::PitchParams;
 use forge_core::{Settings, Source, ORDERS};
 use knurl_core::{Seed, GRIT_OFF, STEPS, STEP_MIN};
 use lathe_core::HARMONICS;
@@ -13,6 +14,26 @@ pub enum SourceParam {
     #[id = "midi"]
     #[name = "MIDI"]
     Midi,
+    #[id = "note"]
+    Note,
+}
+impl From<SourceParam> for Source {
+    fn from(s: SourceParam) -> Self {
+        match s {
+            SourceParam::Audio => Source::Audio,
+            SourceParam::Midi => Source::Midi,
+            SourceParam::Note => Source::Note,
+        }
+    }
+}
+impl From<Source> for SourceParam {
+    fn from(s: Source) -> Self {
+        match s {
+            Source::Audio => SourceParam::Audio,
+            Source::Midi => SourceParam::Midi,
+            Source::Note => SourceParam::Note,
+        }
+    }
 }
 /// The six orders of `ORDERS`, in the same order.
 #[derive(Enum, Debug, PartialEq, Eq, Clone, Copy)]
@@ -281,6 +302,8 @@ pub struct ForgeParams {
     pub editor: Arc<EguiState>,
     #[id = "source"]
     pub source: EnumParam<SourceParam>,
+    #[nested(group = "Pitch")]
+    pub pitch: PitchParams,
     #[id = "gate"]
     pub gate: FloatParam,
     #[id = "order"]
@@ -300,6 +323,7 @@ impl Default for ForgeParams {
         Self {
             editor: EguiState::from_size(forge_ui::WIDTH, forge_ui::HEIGHT),
             source: EnumParam::new("Pitch source", SourceParam::Audio),
+            pitch: PitchParams::default(),
             gate: linear("Gate", d.gate, -60., -20., " dB"),
             order: EnumParam::new("Order", OrderParam::LatheTemperKnurl),
             bypass: BoolParam::new("Bypass", false).make_bypass(),
@@ -401,10 +425,8 @@ impl ForgeParams {
             .unwrap_or(0);
         let curve = self.temper.curve.value();
         let mut s = Settings {
-            source: match self.source.value() {
-                SourceParam::Audio => Source::Audio,
-                SourceParam::Midi => Source::Midi,
-            },
+            source: self.source.value().into(),
+            pitch: self.pitch.pitch(),
             gate: self.gate.value(),
             order: ORDERS[order],
             lathe: lathe_core::Settings {
@@ -576,11 +598,13 @@ impl ForgeParams {
             old.knurl.steps as i32,
             new.knurl.steps as i32,
         );
-        let source = |s: Source| match s {
-            Source::Audio => SourceParam::Audio,
-            Source::Midi => SourceParam::Midi,
-        };
-        switch(setter, &self.source, source(old.source), source(new.source));
+        switch(
+            setter,
+            &self.source,
+            SourceParam::from(old.source),
+            SourceParam::from(new.source),
+        );
+        self.pitch.apply(setter, &old.pitch, &new.pitch);
         let order =
             |s: &Settings| ORDER_PARAMS[ORDERS.iter().position(|o| *o == s.order).unwrap_or(0)];
         switch(setter, &self.order, order(old), order(new));