Refactor gov/proposals/v0 namespace to include the proposals order

[joaosreis]

The order in which proposals were added must be preserved to properly reconstruct the ledger state.
This PR refactors the gov/proposals/v0 canonical namespace definition to also encode the order of each proposal.

[Copilot]

Pull request overview

Refactors the gov/proposals/v0 namespace CDDL so proposal entries can encode insertion order, enabling deterministic reconstruction of ledger state from stored proposals.

Changes:

• Update gov/proposals/v0 record_entry value shape to include an ordering word64 alongside the proposal payload.
• Clarify the gov/proposals/v0 key-size comment (28-byte tx hash + 4-byte tx index + 2-byte proposal index).
• Bump the pinned tweag/CIPs revision across Nix flake inputs, lockfile, and CI checkout to match the updated reference specs.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
scls-cardano/cddl-src/Cardano/SCLS/Namespace/GovProposals.hs	Encodes proposal insertion order in the namespace entry value.
scls-cardano/cddl-src/Cardano/SCLS/CDDL.hs	Updates the key-size comment for gov/proposals/v0 to match the 28/4/2 breakdown.
flake.nix	Updates the pinned tweag/CIPs revision used for reference specs.
flake.lock	Locks the updated tweag/CIPs revision and narHash.
.github/workflows/haskell-ci.yml	Updates CI to checkout the same pinned tweag/CIPs revision.

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