Solidity contracts have no version source — publish pathway is blocked

Problem

Since #76 a contract's publish version comes from its crate's Cargo.toml [package].version — which Solidity contracts don't have. resolveContractVersion (pipeline.ts) deliberately fails the whole deploy for any contract without a version, so the Foundry/Hardhat publish pathway is currently blocked: a Solidity contract with /// @custom:cdm @org/name detects fine, builds fine, and then aborts deploy with an error that (worse) tells the user to edit a Cargo.toml they don't have.

Failing loud was the right interim choice, but Solidity needs a version-source convention.

Proposal

Primary: a NatSpec tag next to the existing package-name tag, keeping version-per-contract exactly like Rust's version-per-crate:

/// @custom:cdm @org/mycontract
/// @custom:cdm-version 1.2.3
contract MyContract { … }

Fallback (or alternative): the project manifest's version (package.json for Hardhat, a [cdm]/custom key in foundry.toml) — but that's per-project, which breaks down for multi-contract repos, so the NatSpec tag should win when both exist.

Same rules as Rust: strict X.Y.Z, not 0.0.0, strictly greater than the registry's latest to publish, up-to-date skip otherwise.

Tasks

• Parse @custom:cdm-version in the Solidity detection path (same place @custom:cdm is read), thread through the build record's version field (already string | undefined — the plumbing exists)
• Fix resolveContractVersion's error text to give toolchain-appropriate advice (Cargo.toml vs NatSpec)
• Template/docs: add the tag to the foundry/hardhat templates and README's Solidity section
• Tests: detection + a pipeline case per toolchain

References

#76 (version source + idempotent deploys); src/lib/contracts/src/pipeline.ts resolveContractVersion; Solidity detection in src/lib/contracts/src/detection.ts / solidity.ts.

Start with src/lib/contracts/src/detection.ts and solidity.ts to trace how @custom:cdm is parsed, then follow the version field into src/lib/contracts/src/pipeline.ts and resolveContractVersion. Review the existing Rust version rules and tests before adding detection and pipeline coverage for Foundry and Hardhat. Done means toolchain-appropriate errors, template and README updates, and passing detection and pipeline tests.