feat(sim): the wire — vendored runtime, route B, headless tests

[Kinflou]

Milestone 1b of playground simulation.

Vendored @comline/runtime

app/src/sim/runtime/ is runtime/src/ from comline-typescript@5c20074, copied verbatim (unpublished workspace package, version 0.0.0 — pinned by copy the way wasm/Cargo.toml pins comline-core by rev). VENDORED.md records the commit and the re-vendor steps. _fixture_chat.ts is the generated chat.ts from the same commit, its @comline/runtime import repointed — it's the drift guard's reference.

transport.ts — the tapped wire

Tap records every frame ({ seq, from, to, bytes, at, kind }) and notifies listeners; TappedTransport wraps one duplex() end and passes send/recv straight through (optional fixed delivery latency). wire(a, b) = a tapped connection between two named endpoints.

generic.ts — route B

GenericClient / GenericDispatch read a ProtocolShape and do what a generated <Proto>Client / <Proto>Dispatcher does — any compiled schema is wireable with no codegen. SimRemoteError maps an err ordinal back to its name via the calling function's throws.

Tests — node --test via tsx

✔ send round-trips a decoded reply (datagram)
✔ send round-trips over JSON-RPC framing
✔ a raised error comes back as SimRemoteError with the ordinal's name
✔ a one-way call sends a request and expects no response
✔ drift guard — GenericDispatch frames match the generated ChatDispatcher

The drift guard runs a send call through GenericDispatch and through the committed generated ChatDispatcher/serveChat on separate tapped wires and asserts the post-handshake frames are byte-identical.

CI runs npm test (Node 22) before the site build; tsconfig.test.json typechecks the sim/ scope with @types/node (kept out of the browser build, which still excludes *.test.ts).

No UI, no app-bundle change — nothing imports sim/ from an entry yet (that's 1d).