The C4→C5 drift bug (hotfix 12556de) was caused by the same RPC
method list being declared twice — once as a zod enum in
worker/entry/types.ts for runtime validation, and once as a TS
union type in runtime-bridge.ts for compile-time handler wiring.
The two drifted when C4 added `invokeInternalTool`: the TS union
grew, the handler switch added a case, but the zod enum was
forgotten, so the runtime gate rejected envelopes the handler had
already registered.
This commit collapses the two declarations into one:
- Extract `workerRpcMethodSchema = z.enum([...])` in
worker/entry/types.ts as the canonical list.
- Export `WorkerRpcMethod = z.infer<typeof workerRpcMethodSchema>`.
- Replace the hand-written `RpcMethod` union in runtime-bridge.ts
with `type RpcMethod = WorkerRpcMethod` plus an explicit import.
- Reuse the schema inside the `rpc-request` variant of
`workerMessageSchema` so adding a method requires exactly one
edit instead of three.
- Add an exhaustiveness `default: { const _exhaustive: never = ... }`
guard to `handleRpc`'s switch. If the zod enum widens without a
matching case, TypeScript fails the build at the `never`
assignment — drift becomes a compile-time error, not a runtime
ZodError fired at the user.
typecheck clean, 529 unit tests green, 8/8 eval green.
ZacharyZhang-NY
43337e535b