feat(contracts): deploy each Honk library once per distinct bytecode

[xgreenx]

RelationsLib and ZKTranscriptLib compile to identical bytecode in both verifier files, yet each circuit deployed its own copy: ~15.8 KB paid twice.

Changes

• deploy::Libraries groups link references by the hash of the library's creation code and deploys each distinct hash once; every file whose copy has that hash links the one address. No version, no list.
• Libraries land through the CREATE2 deployer under an empty salt, so the address is library_address(creation_code); a re-run finds code there and sends nothing.
• circuits::deploy_honk_verifiers(provider, artifacts, &Circuit::ALL, sender) deploys a set and returns HonkVerifiers { verifiers, libraries }. deploy_honk_verifier still works alone.
• Libraries::link returns linked creation code without deploying (factory deploys).
• The circuits.rs doc no longer claims the libraries are unshared.
• Anvil: both circuits in 4 transactions (was 6), 2 library deployments, each verifier's code carries the shared addresses, Initializer hash equals keccak256(code), logN differs.
• LinkFixture.sol links same-named libraries compiled from other code; read from forge out/, its pair deploys beside the circuits' pair.

Verified

• forge test 482 passed; lint and fmt clean.
• nightly fmt, clippy, cargo test --all with anvil: 14 unit + 7 anvil pass; cargo doc clean.

Not verified / known issues

• Keyed by creation code, not runtime code: it is the CREATE2 preimage, and equal creation code is equal runtime code.
• chain-configurations builds on a pin bump; to share it must replace link_creation_code with Libraries::deploy + link.
• A chain without the CREATE2 deployer gets it installed.