Add signing progress, in-flight voiding, and precise provider errors

[jameskurz-filecoin]

Changes

In-flight MNDAs and contracts can now be voided after the counterparty signs, with a required reason and confirmation that the provider copy and partial signatures will be deleted. The shared workflow refreshes and validates the exact provider binding, refuses completed or fully signed copies and signed mismatches, and preserves audit history and retry recovery.

A compact View progress disclosure shows confirmed preparation, approval where needed, sending, signatures, and final PDF storage. Rejected approvals and missing historical evidence no longer look like active progress; single-signer requests omit the counterparty step.

SignWell failures distinguish timeout, access, rate limits, and refused requests. Logs retain only the operation phase, bounded category, and HTTP status. The old generic error did not retain enough information to diagnose the reported production failure, so this change does not claim a cause or a guaranteed duplicate-free outcome.

Validation

• 198 focused shared signing workflow tests; 32 provider transport/adapter tests; failure mapping/action tests and 54 contract UI/error tests; focused UI, domain policy, and catalog regressions.
• Web, workflow, and integration typechecks; scoped lint, formatting, secret checks, and commit hooks.
• Computer-use QA in the local administrator demo: expanded countersignature checklist, compact layout, and Void in the partially signed request menu.
• Independent adversarial reviews of engine, failure handling, and UI. Fixed the rejected-approval issue found during review.

Provider limitation

SignWell offers no documented conditional delete. A signer could complete between the fresh provider read and delete; this pre-existing remote race remains documented. No live documents were sent, signed, or canceled during verification. No external SignWell cancellation qualification was performed in this session. This PR does not include the separate PDF-spacing change in draft #141.