Update to v86 HEAD with IDE shared-register fix

Patches src/ide.js before building: restores the dual master+slave writes
for ATA Command Block registers (Features, Sector Count, LBA Low/Mid/High)
that 1b90d2e7 changed to current_interface-only. Those registers are
channel-shared per ATA spec; Win95's ESDI_506.PDR writes them then switches
drive-select expecting the values to persist. Found via JS-only bisect.

Boots fresh in ~32s with the same sporadic-bluescreen rate as the prod build.
The new build has the tcp-connection bus event so SMB uses the clean path
instead of the connection-theft hack (guard added for the old-API monkeypatch
to skip if the bus handler already accepted).

tools/update-v86.js applies the source patch automatically. v86 checkout
left clean (patch stashed).

.gitignore

@@ -15,3 +15,4 @@ trusted-signing-metadata.json
 .env
 electron-windows-sign.log
 .npmrc
+/.claude/

src/renderer/smb/index.ts

@@ -148,6 +148,10 @@ export function setupSmbShare(emulator: V86, hostPath: string) {
     const orig = adapter.on_tcp_connection.bind(adapter);
     adapter.on_tcp_connection = function (packet: any, tuple: string): boolean {
       if (packet.tcp.dport !== 139) return orig(packet, tuple);
+      // New v86 fires the tcp-connection bus event BEFORE this callback;
+      // if our bus handler already accepted the conn, it's in tcp_conn —
+      // claim it so the original (which would otherwise RST) doesn't run.
+      if (adapter.tcp_conn[tuple]) return true;
 
       const adapterAny = adapter as any;
       adapterAny.receive = () => {};

tools/update-v86.js

@@ -51,10 +51,48 @@ function download(url, dest) {
   });
 }
 
+/**
+ * v86 commit 1b90d2e7 (May 2025) changed ATA Command Block register writes
+ * to only target current_interface instead of both master and slave. Those
+ * registers (ports 0x1F1-0x1F6) are channel-shared per the ATA spec — both
+ * drives on the cable see the same register file. Win95's ESDI_506.PDR
+ * writes them, switches drive-select, expects them to still be there.
+ * Result: IDE IRQ never fires, splash screen hang.
+ *
+ * Found via JS-only bisect: prod wasm + freshly-built libv86.js, parent
+ * 3c944a02 boots, 1b90d2e7 hangs deterministically.
+ */
+function patchIdeSharedRegisters(ideJsPath) {
+  let s = fs.readFileSync(ideJsPath, 'utf-8');
+  const re = /this\.current_interface\.(\w+_reg) = \(this\.current_interface\.\1 << 8 \| data\) & 0xFFFF;/g;
+  const matches = [...s.matchAll(re)];
+  if (matches.length === 0) {
+    console.log('  ide.js: shared-register patch already applied or upstream fixed it');
+    return;
+  }
+  if (matches.length < 5) {
+    throw new Error(`ide.js: expected ≥5 register write sites, found ${matches.length} — pattern changed`);
+  }
+  s = s.replace(re, (_, reg) =>
+    `this.master.${reg} = (this.master.${reg} << 8 | data) & 0xFFFF;\n` +
+    `        this.slave.${reg} = (this.slave.${reg} << 8 | data) & 0xFFFF;`
+  );
+  fs.writeFileSync(ideJsPath, s);
+  console.log(`  ide.js: restored shared-register writes (${matches.length} sites)`);
+}
+
 async function main() {
   const jsDest = path.join(LIB_DIR, 'libv86.js');
   const wasmDest = path.join(LIB_DIR, 'build/v86.wasm');
 
+  // ─── source patch (before any build) ─────────────────────────────────────
+  if (!JS_ONLY) {
+    const ideJs = path.join(V86_DIR, 'src/ide.js');
+    if (fs.existsSync(ideJs)) {
+      patchIdeSharedRegisters(ideJs);
+    }
+  }
+
   // ─── wasm ────────────────────────────────────────────────────────────────
   let wasmDate;
   if (JS_ONLY) {