feat: add hwOverdrive SDP profile override module

packages/web/src/utils/hwOverdrive.ts

@@ -0,0 +1,57 @@
+// packages/web/src/utils/hwOverdrive.ts
+//
+// Self-contained SDP profile override for hardware H.264 encoding.
+// Zero imports from our codebase — operates at the WebRTC API layer.
+
+let _active = false;
+let _originalCreateOffer: typeof RTCPeerConnection.prototype.createOffer | null = null;
+
+function rewriteSdp(sdp: string): string {
+  return sdp.replace(/profile-level-id=(42e01f|42c01f)/gi, 'profile-level-id=4d0032');
+}
+
+/**
+ * Activate the SDP profile override.
+ * Patches RTCPeerConnection.prototype.createOffer to rewrite
+ * H.264 Constrained Baseline (42e01f/42c01f) → Main Profile (4d0032).
+ * No-op if already active.
+ */
+export function activate(): void {
+  if (_active) return;
+
+  _originalCreateOffer = RTCPeerConnection.prototype.createOffer;
+  _active = true;
+
+  // RTCPeerConnection.prototype.createOffer has two overloads in the WebRTC typings.
+  // We cast through unknown to satisfy TypeScript while keeping the runtime shape correct.
+  const patched: typeof RTCPeerConnection.prototype.createOffer = async function (
+    this: RTCPeerConnection,
+    options?: RTCOfferOptions,
+  ): Promise<RTCSessionDescriptionInit> {
+    const offer = await (_originalCreateOffer as (options?: RTCOfferOptions) => Promise<RTCSessionDescriptionInit>).call(this, options);
+    if (_active && offer.sdp) {
+      return { type: offer.type, sdp: rewriteSdp(offer.sdp) };
+    }
+    return offer;
+  } as unknown as typeof RTCPeerConnection.prototype.createOffer;
+
+  RTCPeerConnection.prototype.createOffer = patched;
+}
+
+/**
+ * Deactivate the SDP profile override.
+ * Restores the original createOffer prototype. No-op if not active.
+ */
+export function deactivate(): void {
+  if (!_active) return;
+  if (_originalCreateOffer) {
+    RTCPeerConnection.prototype.createOffer = _originalCreateOffer;
+    _originalCreateOffer = null;
+  }
+  _active = false;
+}
+
+/** Check if the SDP override is currently active. */
+export function isActive(): boolean {
+  return _active;
+}