fix(rivetkit-swift): avoid double percent-encoding paths in URLUtils

[Makisuo]

Re-filing rivet-dev/rivetkit-swift#1 against the monorepo

combineUrlPath builds fullPath from already-encoded segments (buildActorGatewayUrl runs addingPercentEncoding(...) on the actor ID, and the action helpers in RemoteManager do the same on path-injected IDs/keys), then assigns it to URLComponents.path, which runs another encoding pass and turns %3A into %253A.

This is invisible for backends whose actor IDs are URL-safe (file-system driver hex hash, engine UUIDs, etc.), so it slipped through. But @rivetkit/cloudflare-workers formats actor IDs as ${durableObjectId}:${generation}, so : → %3A → %253A. After the round-trip the worker decodes one layer and parseActorId throws Invalid actor ID format: ...e3704%3A0, the WebSocket handshake fails, and the SwiftUI client enters a reconnect loop.

Repro:

1. wrangler dev a @rivetkit/cloudflare-workers registry exposing any actor.
2. Point a SwiftUI client at http://127.0.0.1:8787/api/rivet and trigger an action.
3. PUT /actors succeeds (no encoded segment in the path), then /gateway/{actorId}/connect 500s with Invalid actor ID format. Patched build connects normally and events flow.

The plain API paths (/metadata, /actors, ?namespace=...) have nothing to re-encode, so they're unaffected by the switch to percentEncodedPath. I didn't add a unit test because URLUtils is internal and the existing tests run against a TestServer — happy to add @testable coverage if you'd prefer.