Export package-backed proof workspaces through structured Lean signatures

[williamjblair]

Export an exact FC declaration through Lean-native extraction and pinned package imports. This replaces the source-reconstruction approach in #4951.

flowchart LR
  D[FC declaration] --> L[Lean-native signature]
  L --> G[Shared generator]
  G --> W[Pinned proof workspace]
  W --> C[Comparator qualification]

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Boundary	Preserved behavior
Native exporter	Answers, explicit proof terms and universe parameters; re-elaborated signatures
Shared generator	Structured declarations, package pins and generated Challenge/Solution files
Python controller	Tool acquisition, output validation and source/tool provenance; no Lean parsing
Qualification	Typed Comparator outcomes, Landrun, compatible lean4export, nanoda and AF_UNIX restrictions

Qualified integration: 34580506688 passed all ten exporter fixtures, 100/100 FC100 exports, negative proof checks and sandbox controls using the integrated exporter. The recorded source revision is 1a7a17cb5767a677b67478c22a3107efe46414a8.

Exact PR head: 34586409681 passed at bb87dfb49125af24ba72ddfe5be894a9f4753f87: all ten fixtures, sandbox checks and 100/100 FC100 exports (zero failures). Typed Comparator receipts and logs are retained in the workflow artifact.

Dependencies: generator leanprover/lean-eval-generator#7; typed qualification uses leanprover/comparator#87. Current fork pins are generator e611b55 and Comparator deec4b9. Adopt accepted revisions and rerun affected qualification before declaring those revisions supported.

Merge order: CLI #5386 now carries proof verification (former #5387) and builds on this exporter. Merged with current main on 16 September; all checks pass, including the package export. #4951 stays open as superseded until this replacement lands. Roadmap: #4394.

Export coverage is not proof of FC100 problems or LeanEval catalog admission. Definition-hole answers still require assessment of their mathematical meaning. Logs remain diagnostics, not verification verdicts.