agent/new: parse cwd parameter into CwdOverride

The cwd= parameter in agent/new payloads was not being parsed,
so scripts like ollie-session-here could not set agent cwd on
creation. Now parsed and passed to AgentParams.CwdOverride.

cmd/olliesrv/internal/fs/support.go

@@ -176,6 +176,8 @@ func parseAgentNewRequest(data []byte) agentNewRequest {
 				r.Params.Remote = v
 			case "profile", "agent":
 				r.Params.Profile = v
+			case "cwd":
+				r.Params.CwdOverride = v
 			case "prompt":
 				r.Prompt = v
 			case "parent":