[e2e] cover unversioned Vertex models, versioned config ids, and count-tokens

Extend the agent-network e2e to the Vertex request shapes a customer
actually sends through Claude Code:

- Register the Vertex provider's model under the raw "@version" id the
  Google console documents, so the router's candidate normalization is
  exercised end to end (previously the provider was created with no
  models array, leaving Vertex per-provider matching untested).
- Allowlist the raw "@version" id in the guardrail, so entry
  normalization is exercised against version-stripped request models.
- Drive the unversioned model id (…/models/claude-sonnet-4-5:rawPredict)
  through the tunnel and require 200 — the customer-reported shape.
- Drive the token-count endpoint (…/models/count-tokens:rawPredict, real
  model in the body) via the new harness VertexCountTokens: an
  allowlisted body model must serve 200, a disallowed one must deny 403
  before the upstream.

e2e/agentnetwork/chat_test.go

@@ -104,8 +104,9 @@ func availableProviders() []providerCase {
 }
 
 // providerRequest builds a create request for a matrix provider: enabled, with
-// a uniquely-priced model for body-routed providers and none for the
-// path-routed Vertex (whose model lives in the request path).
+// a uniquely-priced model registered under the id an operator would paste —
+// the normalized catalog id for Bedrock, the raw form elsewhere (including the
+// "@version" Vertex id, which the router must normalize to route).
 func providerRequest(pc providerCase) api.AgentNetworkProviderRequest {
 	req := api.AgentNetworkProviderRequest{
 		Name:        pc.name,
@@ -114,18 +115,15 @@ func providerRequest(pc providerCase) api.AgentNetworkProviderRequest {
 		ApiKey:      &pc.apiKey,
 		Enabled:     ptr(true),
 	}
-	if pc.kind != harness.WireVertex {
-		// The router matches the normalized catalog id. Bedrock's request model
-		// travels as a region-prefixed inference-profile id in the URL path
-		// (us.anthropic...), which the router strips before matching, so register
-		// the normalized form here or routing fails as model_not_routable.
-		modelID := pc.model
-		if pc.kind == harness.WireBedrock {
-			modelID = catalogModel(pc)
-		}
-		req.Models = &[]api.AgentNetworkProviderModel{
-			{Id: modelID, InputPer1k: 0.001, OutputPer1k: 0.002},
-		}
+	// Register Bedrock under its normalized catalog id (the router strips the
+	// region prefix before matching); other providers, incl. the raw "@version"
+	// Vertex id, register as-is so the router's normalization is exercised.
+	modelID := pc.model
+	if pc.kind == harness.WireBedrock {
+		modelID = catalogModel(pc)
+	}
+	req.Models = &[]api.AgentNetworkProviderModel{
+		{Id: modelID, InputPer1k: 0.001, OutputPer1k: 0.002},
 	}
 	return req
 }