v3: Cryptographic ledger signatures (enterprise reconsideration) #4

Summary

Evaluate cryptographic signatures for ledger entries to strengthen provenance guarantees.

Context

Explicit non-goal for v1 per ROADMAP.md. Reconsider for enterprise deployments.

Scope ideas

• Sign ledger entries at write time
• Verify chain integrity on ledger why
• Key management guidance (local keys, CI signing)

Open questions

• Which signature algorithm and key store?
• Backward compatibility with existing .outerloop/ledger/ data