Key under which the kernel terminal handler brands an IRequest with a WebSocket upgrade intent.

Created with Symbol.for, not Symbol(), so two copies of this package in one process resolve the same key — the SECURITY_METADATA precedent.

The IRequest is the channel rather than IRequestContext.state, and that is a correctness requirement rather than a preference: the HTTP adapter holds the IRequest it built and hands to the framework handler, and never sees the IRequestContext — the kernel creates the context internally and discards it when the handler returns. There is no path by which a value written to ctx.state could reach the adapter that must perform the handshake.

Prefer setUpgradeIntent and upgradeIntentOf over touching this directly; the symbol is exported so a custom adapter outside @setu-ts/runtime can read the brand.