feat(payment): commitment binding fields for quote types (ADR-0004)

[grumbach]

Part of ADR-0003: commitment-bound quote pricing — the shared wire-type layer.

What

Adds the signed fields that bind a quote's price to the node's audited storage commitment:

• PaymentQuote and MerklePaymentCandidateNode gain committed_key_count: u32 + commitment_pin: Option<[u8; 32]> (tail-placed, serde-default).
• MerklePaymentProof gains commitment_sidecars: Vec<Vec<u8>>.
• Both signing payloads are extended to cover the new fields — single-node bytes_for_signing and the merkle candidate bytes_to_sign (now 5-field), with the pin tagged (0 = none, 1 = present) so a baseline quote can't collide with one pinning an all-zero hash.

The two fields are covered by the quote signature and the quote hash, so the price a node may charge is tied to how much data it can prove it holds.

Scope

This is only the shared struct/signing change. The node-side pricing + audit and the client-side resolve-before-pay enforcement live in the companion PRs:

• ant-protocol: shared commitment + pricing (depends on this)
• ant-node: node-side forced pricing + audit
• ant-client: resolve-before-pay

Release ordering

This is the first crate in the ADR-0003 release chain — it has no ADR-0003 dependencies and builds standalone. The other three depend on it being published.

This is a breaking quote-format change (the signed payload changes), per the ADR's hard-cutover rollout.

[dirvine]

Reviewed the current head a7ac7e2620cb6a50151dd0c619fd75e03b02f05c for evmlib #11.

Verified:

• Cargo.toml is bumped to 0.9.0 for the breaking signed quote/wire-format change.
• CHANGELOG.md documents ADR-0004 and the hard-cutover signature incompatibility.
• PaymentQuote::bytes_for_signing covers committed_key_count and a tagged commitment_pin (None vs Some([0; 32]) cannot collide).
• PaymentQuote::hash continues to include the signed payload plus pubkey/signature, so the new binding fields are hash-covered.
• MerklePaymentCandidateNode::bytes_to_sign and to_bytes include the same count/pin binding, so Merkle candidate signatures and pool hashes bind the new fields.
• Current CI is green: 7/7 checks pass, including dry-run publish.

Local note: cargo test --all --no-fail-fast builds, but Anvil-dependent tests fail locally because anvil is not installed on this runner (SpawnFailed: No such file or directory). Non-Anvil tests that ran passed; GitHub CI has the pinned Foundry setup and is green.

No code issues found in this crate. The remaining blockers from the earlier package review are downstream in ant-protocol/ant-node/ant-client, not in evmlib.

Minor non-blocking nit: the PR body still says ADR-0003 in a few places while the committed files now say ADR-0004.