Sync Canvas LMS export feature + refreshed Settings screenshot

Brings the share build up to date with the main project: QTI .zip export
and optional direct Canvas API push, plus the Canvas settings card.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/canvas/zip.js

@@ -0,0 +1,99 @@
+// lib/canvas/zip.js — minimal, zero-dependency ZIP writer (STORE method, no compression).
+// Canvas accepts uncompressed QTI packages, so we skip DEFLATE entirely and avoid any
+// dependency. Output is a standard .zip as a Uint8Array. Deterministic (fixed timestamps).
+
+const CRC_TABLE = (() => {
+  const t = new Uint32Array(256);
+  for (let n = 0; n < 256; n++) {
+    let c = n;
+    for (let k = 0; k < 8; k++) c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1;
+    t[n] = c >>> 0;
+  }
+  return t;
+})();
+
+// CRC-32 (IEEE 802.3). crc32 of "123456789" === 0xCBF43926 (unit-test anchor).
+export function crc32(bytes) {
+  let c = 0xffffffff;
+  for (let i = 0; i < bytes.length; i++) c = CRC_TABLE[(c ^ bytes[i]) & 0xff] ^ (c >>> 8);
+  return (c ^ 0xffffffff) >>> 0;
+}
+
+const enc = new TextEncoder();
+const toBytes = (data) => (typeof data === "string" ? enc.encode(data) : data);
+
+// files: [{ name: string, data: string|Uint8Array }] -> Uint8Array (.zip bytes)
+export function storeZip(files) {
+  const DOS_TIME = 0;
+  const DOS_DATE = 0x0021; // 1980-01-01, deterministic
+  const chunks = [];
+  const central = [];
+  let offset = 0;
+
+  for (const f of files) {
+    const nameBytes = enc.encode(f.name);
+    const data = toBytes(f.data);
+    const crc = crc32(data);
+
+    const local = new Uint8Array(30 + nameBytes.length);
+    const lv = new DataView(local.buffer);
+    lv.setUint32(0, 0x04034b50, true); // local file header signature
+    lv.setUint16(4, 20, true);         // version needed to extract
+    lv.setUint16(6, 0x0800, true);     // flags: bit 11 = UTF-8 filenames
+    lv.setUint16(8, 0, true);          // compression method 0 = store
+    lv.setUint16(10, DOS_TIME, true);
+    lv.setUint16(12, DOS_DATE, true);
+    lv.setUint32(14, crc, true);
+    lv.setUint32(18, data.length, true); // compressed size (== uncompressed for store)
+    lv.setUint32(22, data.length, true); // uncompressed size
+    lv.setUint16(26, nameBytes.length, true);
+    lv.setUint16(28, 0, true);           // extra field length
+    local.set(nameBytes, 30);
+    chunks.push(local, data);
+
+    const cd = new Uint8Array(46 + nameBytes.length);
+    const cv = new DataView(cd.buffer);
+    cv.setUint32(0, 0x02014b50, true); // central directory header signature
+    cv.setUint16(4, 20, true);   // version made by
+    cv.setUint16(6, 20, true);   // version needed
+    cv.setUint16(8, 0x0800, true);
+    cv.setUint16(10, 0, true);   // method
+    cv.setUint16(12, DOS_TIME, true);
+    cv.setUint16(14, DOS_DATE, true);
+    cv.setUint32(16, crc, true);
+    cv.setUint32(20, data.length, true);
+    cv.setUint32(24, data.length, true);
+    cv.setUint16(28, nameBytes.length, true);
+    cv.setUint16(30, 0, true);   // extra length
+    cv.setUint16(32, 0, true);   // comment length
+    cv.setUint16(34, 0, true);   // disk number start
+    cv.setUint16(36, 0, true);   // internal attributes
+    cv.setUint32(38, 0, true);   // external attributes
+    cv.setUint32(42, offset, true); // relative offset of local header
+    cd.set(nameBytes, 46);
+    central.push(cd);
+
+    offset += local.length + data.length;
+  }
+
+  const centralStart = offset;
+  let centralSize = 0;
+  for (const cd of central) { chunks.push(cd); centralSize += cd.length; }
+
+  const eocd = new Uint8Array(22);
+  const ev = new DataView(eocd.buffer);
+  ev.setUint32(0, 0x06054b50, true); // end of central directory signature
+  ev.setUint16(8, central.length, true);  // entries on this disk
+  ev.setUint16(10, central.length, true); // total entries
+  ev.setUint32(12, centralSize, true);
+  ev.setUint32(16, centralStart, true);
+  ev.setUint16(20, 0, true); // comment length
+  chunks.push(eocd);
+
+  let total = 0;
+  for (const c of chunks) total += c.length;
+  const out = new Uint8Array(total);
+  let p = 0;
+  for (const c of chunks) { out.set(c, p); p += c.length; }
+  return out;
+}