fix(api,makefile): gofmt bearer_token_grpc and lowercase kind cluster slug

- gofmt bearer_token_grpc.go (was failing CI lint check)
- Lowercase CLUSTER_SLUG before sed processing so branch names like HEAD
  produce valid kind cluster names (kind requires lowercase alphanumeric)

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: markturansky

Makefile

@@ -76,7 +76,7 @@ KIND_IMAGE_PREFIX := $(if $(filter podman,$(CONTAINER_ENGINE)),localhost/,)
 # Kind cluster configuration — derived from git branch for multi-worktree support
 # Each worktree/branch gets a unique cluster name and ports automatically.
 # Override any variable: make kind-up KIND_CLUSTER_NAME=ambient-custom KIND_FWD_FRONTEND_PORT=8080
-CLUSTER_SLUG ?= $(shell git rev-parse --abbrev-ref HEAD 2>/dev/null | sed 's/[^a-zA-Z0-9]/-/g' | sed 's/--*/-/g' | sed 's/^-//' | sed 's/-$$//' | cut -c1-20)
+CLUSTER_SLUG ?= $(shell git rev-parse --abbrev-ref HEAD 2>/dev/null | tr '[:upper:]' '[:lower:]' | sed 's/[^a-z0-9]/-/g' | sed 's/--*/-/g' | sed 's/^-//' | sed 's/-$$//' | cut -c1-20)
 CLUSTER_SLUG := $(CLUSTER_SLUG)
 KIND_CLUSTER_NAME ?= ambient-$(CLUSTER_SLUG)
 KIND_CLUSTER_NAME := $(KIND_CLUSTER_NAME)

components/ambient-api-server/pkg/middleware/bearer_token_grpc.go

@@ -61,4 +61,3 @@ type serviceCallerStream struct {
 func (s *serviceCallerStream) Context() context.Context {
 	return s.ctx
 }
-