Complete public fixtures and four missing answer contracts

[ma7dev]

Changes

• Publish/reproduce version 2026.09.27.1 with all 6,089 cases and 11 public fixture files.
• Document four source-based Absher annotations: two answer-key repairs and two ambiguous-question corrections using the recorded meanings.
• Preserve original prompts, blank upstream answer cells, pinned CSV hashes/row indexes, and annotation rationale in the public ledger.
• Update dataset card, README and reconstruction CI. Historical reconstruction remains unchanged.

Verification

29 tests; Ruff; clean deterministic rebuild; exactly four changed rows and two changed prompts; published file hashes independently downloaded and verified.