Throw specific error types when calling functions that are relesed or…

[andrewmcgov]

What

@remote-ui/rpc serializes functions as revocable RPC proxies. Calling a proxy after its target was released, or after the endpoint was terminated, previously threw a generic Error whose only signal was a message string.

This PR introduces two exported Error subclasses thrown from createBasicEncoder (packages/rpc/src/encoding/basic.ts):

• RemoteFunctionReleasedError — use-after-free: the call() site when the target function is gone, and the proxy when it's already been released.
• RemoteFunctionRevokedError — the proxy was revoked because the endpoint was terminated.

Both follow the existing MissingResolverError pattern (extends Error, sets this.name) and are re-exported from the package root.

Why

Consumers currently string-match message.includes('already released' | 'already revoked') to triage these in error reporting. With named types, consumers can use instanceof (or the stable error.name) and tell the two cases apart.