fix: remove unknown/unknown platform entries from Docker manifests

Add provenance: false to docker/build-push-action to prevent BuildKit
from generating SLSA attestation entries that appear as unknown/unknown
in the image manifest.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/bump.yml

@@ -91,6 +91,7 @@ jobs:
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
+          provenance: false
           cache-from: type=gha
           cache-to: type=gha,mode=max
 

.github/workflows/release.yml

@@ -51,6 +51,7 @@ jobs:
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
+          provenance: false
           cache-from: type=gha
           cache-to: type=gha,mode=max