Define signed Every Code agent provenance and verifier vectors

[shiny-code-bot]

Goal

Implement the signed Every Code agent-run provenance wire contract, signing/verifying library, key material, replay/role-conflict ledger, and deterministic cross-language test vector required by parent #441.

Scope

• Add a new Every Code-owned Rust crate for provenance claims, challenge binding, Ed25519 compact JWS signing/verifying, runtime-controlled model-family derivation, transcript digesting, and issuance ledger behavior.
• Bind audience, nonce, canonical challenge digest, repository, PR when available, head/tree SHA, run role, root/session/thread/turn identity, runtime model/family/provider, task identity, issue/expiry times, and evidence digest.
• Keep policy decisions outside Every Code.
• Generate a deterministic golden token/JWKS/negative-vector fixture that Launchplane can verify independently.
• Do not add the final code exec or CLI export surface in this issue.

Acceptance Criteria

• Signature, issuer, audience, expiry, nonce, challenge, repo/PR/head, role, run identity, and model-family tampering fail verification.
• One run cannot be issued under both implementer and reviewer roles or replayed as a second run.
• Model identity comes from observed runtime metadata, never challenge or caller text.
• Raw remote URLs and transcript contents are never emitted.
• The golden vector is deterministic and suitable for a PyJWT Launchplane verifier test.
• ./build-fast.sh passes with no warnings.

Finish Line

Every Code has a tested signed provenance library and stable cross-language verifier vector.

Next Action

Add the crate and fixed-clock golden vector around existing Ed25519 and agent/session identity primitives.

[shiny-code-bot]

Closed as not planned on August 6, 2026. The reviewed contract and closed PR #444 were produced in a retired repository and will not be merged or migrated as code. Their useful requirements—server-owned exact-target binding, replay resistance, bounded evidence, and fail-closed evaluation—have been restated in cbusillo/launchplane#2011. Launchplane now owns dispatch and verification directly, so a signed runtime contract is unnecessary for the current trust boundary.