Follow-up: PR #4005 doc-drift chores (ABI version, README, error taxonomy addendum)

[piotr-roslaniec]

Context

PR #4005 (multi-agent review report at agent-docs/reviews/pr-4005/report.md) surfaced 3 doc-drift chores that should land with the implementation work. These are simple, mechanical changes.

Chores

1. README.md: ABI version drift

• The PR description and PR title say "FFI ABI 2.0".
• pkg/tbtc/signer/src/lib.rs:17 carries TBTC_SIGNER_ABI_MAJOR = 4.
• Fix: update the PR description and title to say "FFI ABI 4.0". Verify any README mentions of "ABI 2.0" or "ABI 2.0 after deletion" are also updated.

2. README.md: removed coarse operations

• The "Current scope" section lists RunDKG, StartSignRound, FinalizeSignRound as coarse operations keyed by session_id.
• These functions have no #[no_mangle] export anywhere in src/lib.rs, src/ffi.rs, or src/api.rs.
• Fix: replace "Current scope" with a description of the actual ABI 4.0 operations (frost_tbtc_dkg_session_run, frost_tbtc_dkg_session_advance, frost_tbtc_interactive_session_*, etc.). Move the removed coarse operations to a "Transitional" or "Removed" section.

3. Phase 0 §8 error taxonomy addendum

• The Phase 0 spec (docs/roast-phase-0-spec-freeze.md §8) does not include:
  • consumed_nonce_replay (Phase 7 §4)
  • interactive_attempt_already_aggregated (Phase 7 §5)
• The implementation uses these error codes at the FFI boundary but the spec has no authoritative source.
• Fix: add an addendum to docs/roast-phase-0-spec-freeze.md §8 (or a separate ADR) listing the new error codes. Update the error taxonomy table.

Acceptance criteria

• README "Current scope" accurately describes the current ABI 4.0 operations.
• All references to "ABI 2.0" in the PR title, description, and README are updated to "ABI 4.0".
• Phase 0 §8 includes consumed_nonce_replay and interactive_attempt_already_aggregated with the correct wire names.
• A separate ADR (docs/adr/) is published if the spec-freeze cannot be amended directly.

Related

• PR feat(tbtc/signer): Rust FROST/ROAST signer (distributed DKG, interactive-only signing, FFI ABI 2.0) #4005 gap-inventory: chores section
• Multi-agent review report: agent-docs/reviews/pr-4005/raw/documentation-A.md, spec-compliance-A.md

[linear]

ENG-749