#30832 Add Swift tests for Cloud repository forwarding

Adds Swift tests for the Cloud repository forwarding contract introduced by the Cloud repository UI: action and parameter allowlists, session binding and overwrite, local-vs-machine sync routing, and Cloud chat/session refusal behavior. Production forwarding remains unchanged.

Validation runs the focused AgentPaneCloudRepositoryTests suite through cmux-ci.

Follow-up for #30688 and #30357.

Agent session: agent session

---

^{Need help on this PR? Tag @codesmith-bot with what you need.}

---

Summary by cubic

Adds Swift tests covering the Cloud repository forwarding contract: method and parameter allowlists, session binding and overwrite, local-vs-remote sync routing, refusal of remote actions outside Cloud chat or without a bound session, and attach frame encoding with surface and params. Production forwarding code is unchanged.

Follow-up for #30688 and #30357.