Rebuild as single-file offline BIP84 wallet

Replace the SvelteKit/daisyUI prototype with a vanilla JS + hand-rolled CSS
app that Bun bundles (code + scure/noble crypto + QR + CSS) into one
self-contained dist/index.html runnable offline from file://.

Wallet core (src/wallet.js):
- BIP84 native-segwit HD wallet from BIP39 seed (+optional passphrase)
- gap-limit scan of receive/change chains, aggregate balance, tx history
- fresh receive/change addresses; signs with witnessUtxo only (enables
  offline signing with no prev-tx fetch)
- coin selection + fee estimation via btc-signer selectUTXO; send-max;
  manual coin control
- offline JSON snapshot export/import (keyless) + signed-tx hex/QR export
- realtime mempool.space WebSocket: track-addresses -> debounced auto
  refresh of balances/history (no polling); live status badge

UI (src/app.js): clean light paper-wallet; create (with optional, skippable
backup verification) / import flow; receive (QR) / send / history / coins /
tools tabs; clickable logo returns home.

API (src/api.js): mempool.space wrapper with retry/backoff for scan-burst
rate limiting; single network choke-point for offline enforcement.

Verified: BIP84 spec vectors, build/sign/parse for auto/max/manual flows,
snapshot roundtrip, live scan + WebSocket, headless-Chrome UI smoke tests.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

1 files changed, 27 insertions, 0 deletions

diff --git a/src/qr.js b/src/qr.js
new file mode 100644
index 0000000..eab74a7
--- /dev/null
+++ b/src/qr.js
@@ -0,0 +1,27 @@
+// QR rendering via the zero-dependency `qrcode-generator` library, output as a
+// crisp SVG path (scales perfectly, no canvas, prints well on a paper wallet).
+
+import qrcode from 'qrcode-generator';
+
+export function qrSvg(text, { margin = 2 } = {}) {
+  const qr = qrcode(0, 'M'); // type 0 = auto-size, error correction M
+  qr.addData(text);
+  qr.make();
+
+  const count = qr.getModuleCount();
+  const size = count + margin * 2;
+
+  let path = '';
+  for (let r = 0; r < count; r++) {
+    for (let c = 0; c < count; c++) {
+      if (qr.isDark(r, c)) {
+        path += `M${c + margin},${r + margin}h1v1h-1z`;
+      }
+    }
+  }
+
+  return `<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 ${size} ${size}" shape-rendering="crispEdges" class="qr">
+    <rect width="${size}" height="${size}" fill="#fff"/>
+    <path d="${path}" fill="#111"/>
+  </svg>`;
+}