Add SemanticLayer.raise_for_access(), mirroring the existing
SemanticView.raise_for_access(), and call it from the layer GET, runtime
schema, and views endpoints before returning or exercising a layer's
decrypted configuration. Previously these endpoints resolved the layer by
UUID with no per-object permission check.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>