chore: re-point trust-kernel dep — echidna-core-spark is now echidna-core-creusot, trust types live in echidna-core 0.2.0 #173

Context

echidnabot's trust kernel is a git dependency pinned by full rev:

echidna-core-spark = { git = "https://github.com/hyperpolymath/echidna", rev = "b761b3a832981be51d4e88076ef1b90fe5037e9c" }

with a comment recording the follow-up: "At this rev the crate is still named echidna-core-spark; it is being renamed echidna-core-creusot upstream, and the trust types are meant to move into echidna-core proper. Follow-up: re-point this line once that lands on echidna main."

Both changes have now landed on echidna main (verified 2026-10-09 during estate recon, PR hyperpolymath/echidna#415):

• crates/echidna-core-creusot/ — the renamed Creusot-annotated trust kernel (axiom_tracker, pareto, compute_trust_level, TrustLevel)
• crates/echidna-core/ 0.2.0 — the stable consumable surface, whose lib docs name echidnabot as an intended client. It re-exports the trust kernel unchanged as echidna_core::trust (so echidna_core::trust::axiom_tracker::AxiomTracker, echidna_core::trust::compute_trust_level, …), plus ProverKind and a strict echidna.prove.result/1 parser (echidna_core::prove_result::ProveResult). Stability policy + git-dependency recipe: crates/echidna-core/README.adoc in the echidna repo.

Task

1. Swap the dependency in Cargo.toml to echidna-core (the stable surface), pinned by full rev on echidna main at the time of the change — never an unmerged branch (per docs/ECHIDNA-INTEGRATION.adoc).
2. Update the use paths:
   • echidna_core_spark::compute_trust_level → echidna_core::trust::compute_trust_level (src/trust/confidence.rs)
   • echidna_core_spark::axiom_tracker::AxiomTracker → echidna_core::trust::axiom_tracker::AxiomTracker (src/trust/axiom_tracker.rs)
3. Delete the follow-up notes once landed (the Cargo.toml comment and the "Follow-up: crate rename" section of docs/ECHIDNA-INTEGRATION.adoc); record the new rev there.
4. Keep echidnabot's local slug ProverKind and local prove_result parser: docs/ECHIDNA-INTEGRATION.adoc deliberately avoids depending on echidna's identifiers/contract types to keep release cadences decoupled. Do not widen scope without an owner ruling.

Acceptance

• cargo build + cargo test green (note: main is red on all three required checks: opentelemetry 0.33 split from tracing-opentelemetry, and RUSTSEC-2026-0285 (rustls) #166 — main may be red on opentelemetry/rustls; coordinate with that, don't stack unrelated breakage)
• Trust level + source axiom-scan behaviour unchanged (existing unit tests in src/trust/ cover both modules)
• STATE/descriptile update per session protocol; conventional commit