cip: add SV governance voter authority

[ericmann]

Summary

This PR adds a Standards Track / Daml CIP specifying an SV governance-voter authority path for non-operational governance votes.

The CIP preserves one-vote-per-SV semantics while separating governance voting from node-operation authority. It defines a DSO-signed SvGovernanceVoter binding, confirmation-quorum rotation through SRARC_RotateGovernanceVoter, optional governance-voter paths on the existing DsoRules_RequestVote and DsoRules_CastVote choices, vote attribution fields, stale-binding handling at close, and cleanup for duplicate or orphaned bindings.

Per CIP-0000, the author has not self-assigned a number; the editor will assign one on merge.

What this CIP specifies

• A DSO-signed SvGovernanceVoter binding for the represented SV's active governance voter.
• Default self-binding at SV onboarding (governanceVoter == sv).
• Governance-voter rotation through the existing confirmation-quorum flow.
• A hardcoded Phase 1 action allowlist via isGovernanceVoterAction.
• Optional bindingCid / castBy arguments on existing request and cast choices to select the governance-voter path.
• Vote attribution via optional castBy, castByRole, and bindingCid fields.
• Stale-binding filtering in DsoRules_CloseVoteRequest.
• Garbage collection for duplicate or orphaned governance-voter bindings.
• One-vote-per-SV tallying with no additional vote weight for governance voters.

What this CIP does not propose

• No changes to vote weight, tokenomics, fees, rewards, or amulet semantics.
• No broad rights-holder voting or multiple ledger-level voters per SV.
• No standalone governance dApp specification.
• No wallet/provider selection, deployment packaging, or UX rollout standard.
• No special target-SV exclusion for SRARC_OffboardSv; represented-SV voting semantics are preserved.

Reference implementation

Reference implementation: canton-network/splice#5533

Relevant artifacts:

• daml/splice-dso-governance/daml/Splice/DSO/GovernanceVoter.daml
• daml/splice-dso-governance/daml/Splice/DsoRules.daml
• daml/splice-dso-governance-test/daml/Splice/Scripts/TestGovernance.daml
• docs/src/sv_operator/sv_governance_voter.rst

Test plan

• Editorial review in this repo.
• Reference implementation reports splice-dso-governance-test-daml/damlTest passing on the linked Splice branch.