Keep checkpoints aligned with PromptKit profiles

internal/framework/llm/checkpoint_fingerprint.go

@@ -0,0 +1,14 @@
+package llm
+
+// CheckpointFingerprint is a stable, non-secret semantic identity contributed
+// by the LLM runtime before pipeline execution.
+type CheckpointFingerprint struct {
+	Name  string
+	Value string
+}
+
+// CheckpointFingerprintProvider exposes LLM-runtime identities that must
+// participate in checkpoint composition.
+type CheckpointFingerprintProvider interface {
+	LLMCheckpointFingerprints() ([]CheckpointFingerprint, error)
+}