feat(echidnabot): consume typed VerifyOutcome + mode/smtStatus from echidna GraphQL (follow-up to echidna#180)

[hyperpolymath]

Context

echidna#180 / echidna PR #188 added the three GraphQL operations (verifyProof, suggestTactics(prover/context/goalState), proverStatus) the echidnabot client expects, and also surfaced the typed REST /api/verify taxonomy through GraphQL:

• new GraphQL enum VerifyOutcome with variants PROVED / NO_PROOF_FOUND / INVALID_INPUT / UNSUPPORTED_FEATURE / TIMEOUT / INCONSISTENT_PREMISES / PROVER_ERROR / SYSTEM_ERROR
• new fields on VerifyProofResult: outcome: VerifyOutcome!, mode: String, smtStatus: String

This issue tracks the echidnabot-side work to consume the new typed fields. The current client (bots/echidnabot/src/dispatcher/echidna_client.rs) only deserializes status / message / proverOutput / durationMs / artifacts from GraphQL and the bare valid: bool from REST, dropping the typed taxonomy in both transports.

What to do

In bots/echidnabot/src/dispatcher/echidna_client.rs:

1. Extend VerifyProofData with optional outcome: Option<String> (or a typed enum mirroring the new server-side enum), mode: Option<String>, smt_status: Option<String>. Update the GraphQL query string in verify_proof_graphql to request the new fields.
2. Extend RestVerifyResponse identically — the REST handler has been emitting these fields since the 2026-04-17 typed-outcome work; the client currently silently discards them (seam-audit sub-finding in echidna#180).
3. Wire the typed outcome into ProofResult so downstream consumers can distinguish Timeout from Failed without re-parsing the message string. The existing parse_proof_status heuristic stays as a fallback for when outcome is None (older echidna servers).
4. Add a unit test that round-trips a VerifyOutcome::TIMEOUT and asserts it lands as ProofStatus::Timeout on the bot side.

Out of scope

• The new suggestTactics(prover, context, goalState) mutation — the client already issues this exact query in suggest_tactics_graphql; once echidna PR chore(deps): bump pulldown-cmark from 0.13.3 to 0.13.4 in /bots/glambot #188 lands it just starts working.
• The new proverStatus query — same: the client already issues it.
• The EchidnaApiMode::Auto retry-after-failure behaviour — out of scope, separate issue if it needs tuning.

Don't

• Don't touch src/abi/ (owner-intentional broken namespace per memory entry [echidna src/abi/ namespace intentional]).

Filed because

GitHub does not auto-close cross-repo Closes references, per the estate memory entry [Cross-repo Closes keyword doesn't auto-fire]. This issue parks the follow-up that echidna PR #188 unblocks.