Initial commit of a toy analogue audio generator

Key components:
- no_std core so it can be used bare metal on embedded systems
- default implementation for RPi 2350, with midi input and I2s output using PIO
- Visualiser for the web to play with on a dev system

www/bootstrap.js

@@ -0,0 +1,72 @@
+/**
+ * bootstrap.js — ES module entry point.
+ *
+ * Imports the wasm-pack-generated glue, initialises the WASM binary, then
+ * wires up Rust-exported types to the canvas elements in index.html.
+ */
+
+import init, {
+    AudioEngine,
+    OscilloscopeView,
+    SpectrumView,
+    PatchBay,
+    SynthParams,
+} from "./pkg/synth_visualiser.js";
+
+const loader    = document.getElementById("loader");
+const status    = document.getElementById("status");
+const srLabel   = document.getElementById("sample-rate");
+const frameTime = document.getElementById("frame-time");
+
+async function bootstrap() {
+    try {
+        await init();
+
+        const engine = new AudioEngine();
+        await engine.attach();
+
+        const analyser    = engine.analyser_node();
+        const oscilloscope = new OscilloscopeView("oscilloscope-canvas", analyser);
+        const spectrum     = new SpectrumView("spectrum-canvas", analyser);
+        const patchbay     = new PatchBay("patchbay-canvas");
+
+        // Register module jacks (x, y coordinates relative to the canvas)
+        patchbay.register_jack("vco",    "out",    50,  60, true);
+        patchbay.register_jack("filter", "in",    150,  60, false);
+        patchbay.register_jack("filter", "out",   250,  60, true);
+        patchbay.register_jack("vca",    "in",    350,  60, false);
+        patchbay.register_jack("lfo",    "cv-out", 450, 60, true);
+        patchbay.register_jack("filter", "cv-in",  550, 60, false);
+
+        const pbCanvas = document.getElementById("patchbay-canvas");
+        pbCanvas.addEventListener("pointerdown", e => patchbay.on_pointer_down(e.offsetX, e.offsetY));
+        pbCanvas.addEventListener("pointermove", e => patchbay.on_pointer_move(e.offsetX, e.offsetY));
+        pbCanvas.addEventListener("pointerup",   e => patchbay.on_pointer_up(e.offsetX, e.offsetY));
+
+        const params = new SynthParams();
+        engine.set_params(params.to_json());
+
+        srLabel.textContent = `SR: ${engine.sample_rate()} Hz`;
+        status.textContent  = "Running";
+        engine.start();
+
+        let last = performance.now();
+        function frame(now) {
+            oscilloscope.draw();
+            spectrum.draw();
+            patchbay.draw();
+            frameTime.textContent = `frame: ${(now - last).toFixed(1)} ms`;
+            last = now;
+            requestAnimationFrame(frame);
+        }
+        requestAnimationFrame(frame);
+
+        loader.classList.add("hidden");
+
+    } catch (err) {
+        console.error("[bootstrap] Fatal:", err);
+        loader.textContent = `Error: ${err.message ?? err}`;
+    }
+}
+
+bootstrap();