feat(governance): let proposer cancel a collective proposal early

[gilescope]

Overview

Adds a cancel_proposal extrinsic to a new pallet, pallet-collective-proposer-cancel, wired as two instances — CouncilProposerCancel and TechnicalCommitteeProposerCancel. Each instance lets the original proposer withdraw their pallet_collective proposal without waiting out the 5-day voting window or organising enough NO votes for early disapproval.

Why

pallet_collective::disapprove_proposal and kill are gated on EnsureRoot, and Root on this chain only comes via a successful federated motion (a 5-day vote). That meant an obviously-bad proposal could not be cleared cheaply by its own author — the only options were marshalling NO votes or waiting out the window. This was raised in chat: "We have no clean way to cancel a proposal early… was it a design choice or should we implement a workaround?". This PR adds the workaround: a tightly-scoped extrinsic that only the original proposer can call.

How

• New crate pallets/collective-proposer-cancel (instance-generic over a pallet_collective::Config<I>). The cancel_proposal(hash) extrinsic looks the proposer up in pallet_collective::CostOf, verifies the caller matches, releases any held deposit, and calls pallet_collective::Pallet::do_disapprove_proposal.
• For the lookup to work, the runtime must record the proposer in CostOf. Both collective instances previously had Consideration = (), which causes is_none() == true and CostOf is never written. They now use runtime_common::governance::RecordProposer — a tiny no-deposit MaybeConsideration impl that returns is_none() == false so the (AccountId, _) row is stored. No deposit is taken; encoded size is unchanged from the unit type.
• The fail mode is documented: with Consideration = () (or any MaybeConsideration whose is_none() == true), cancel_proposal always returns ProposerNotRecorded.
• DisapproveOrigin/KillOrigin remain EnsureRoot — the new path doesn't widen Root's blast radius, it just adds an orthogonal proposer-only path that cannot affect anyone else's proposal.

🗹 TODO before merging

• Reviewer to comment /bot rebuild-metadata on this PR — adding pallets and changing CostOf's value type means runtime metadata must be regenerated.
• Ready

📌 Submission Checklist

• All commits are signed off (git commit -s) for the DCO
• Changes are backward-compatible (or flagged if breaking)
• Pull request description explains why the change is needed
• Self-reviewed the diff
• I have included a change file, or skipped for this reason:
• If the changes introduce a new feature, I have bumped the node minor version
• Update documentation (if relevant)
• Updated AGENTS.md if build commands, architecture, or workflows changed
• No new todos introduced

🧪 Testing Evidence

Unit tests in pallets/collective-proposer-cancel/src/tests.rs cover:

• proposer can cancel their own proposal (storage cleared, event emitted)
• non-proposer call → NotProposer, original storage intact
• bogus hash → ProposalMissing
• proposal closed via normal vote → subsequent cancel returns ProposalMissing
• double-cancel → second call returns ProposalMissing

cargo test -p pallet-collective-proposer-cancel
test result: ok. 7 passed; 0 failed

cargo clippy -p midnight-node-runtime -p pallet-collective-proposer-cancel -p runtime-common --all-targets — clean.

• Additional tests are provided (if possible)

🔱 Fork Strategy

• Node Runtime Update
• Node Client Update
• Other:
• N/A

Links

[jacek-kurkowski-shielded]

Hi @gilescope !

It seems that it fails with Transaction call is not expected.