Add popup help to elements

crates/synth-core/src/oscillator.rs

@@ -37,6 +37,16 @@ impl Vco {
             ParamDescriptor { id: "freq_hz",  label: "Freq", min: 20.0, max: 20_000.0, default: 440.0, unit: "Hz", labels: &[] },
             ParamDescriptor { id: "waveform", label: "Wave", min: 0.0,  max: 4.0,      default: 1.0,   unit: "",   labels: &["Sine", "Saw", "Sqr", "Tri", "Pls"] },
         ],
+        description: "\
+## VCO — Voltage-Controlled Oscillator
+
+Generates a periodic audio-rate waveform at the set frequency.
+
+**Waveforms:** Sine · Saw · Square · Triangle · Pulse
+
+**Freq** sets the base pitch. Connect an LFO or keyboard CV to `cv_freq_hz` for 1 V/oct pitch modulation (0 V = 440 Hz, +1 V = 880 Hz).
+
+**Typical chain:** VCO Out → Filter In → VCA In → Output In",
     };
 
     #[inline]