Add audio nodes to the patch bay

Also make the patch bay responsive.

crates/synth-core/src/envelope.rs

@@ -1,6 +1,7 @@
 //! ADSR envelope generator.
 
 use crate::{AudioProcessor, config::SampleRate};
+use crate::descriptor::{ComponentDescriptor, Direction, JackDescriptor, ParamDescriptor, SignalKind};
 
 #[derive(Clone, Copy, Debug, PartialEq)]
 enum Stage { Idle, Attack, Decay, Sustain, Release }
@@ -25,6 +26,21 @@ impl Adsr {
         }
     }
 
+    pub const DESCRIPTOR: ComponentDescriptor = ComponentDescriptor {
+        kind: "adsr",
+        label: "ADSR",
+        jacks: &[
+            JackDescriptor { id: "gate_in", label: "Gate", direction: Direction::Input,  signal: SignalKind::Gate },
+            JackDescriptor { id: "env_out", label: "Env",  direction: Direction::Output, signal: SignalKind::Cv   },
+        ],
+        params: &[
+            ParamDescriptor { id: "attack_s",  label: "Attack",  min: 0.001, max: 4.0, default: 0.01, unit: "s" },
+            ParamDescriptor { id: "decay_s",   label: "Decay",   min: 0.001, max: 4.0, default: 0.1,  unit: "s" },
+            ParamDescriptor { id: "sustain",   label: "Sustain", min: 0.0,   max: 1.0, default: 0.7,  unit: ""  },
+            ParamDescriptor { id: "release_s", label: "Release", min: 0.001, max: 8.0, default: 0.3,  unit: "s" },
+        ],
+    };
+
     pub fn gate_on(&mut self)  { self.stage = Stage::Attack; }
     pub fn gate_off(&mut self) { self.stage = Stage::Release; }
     pub fn is_idle(&self) -> bool { self.stage == Stage::Idle }