Source-Informed Fuzzing of Sledgehammer's External ATP Interface

Reproduction artifact accompanying the paper "Validating the Verifier: Automated Testing for Isabelle/HOL Proof Assistant" (2026, Section 3.4 / 4.4).

Contains the Python harnesses, shell drivers, and result archives used to identify three previously-unknown defects on the normal Sledgehammer call path:

• Bug 1: TPTP keyword collision (atp_problem.ML / Zipperposition Lex_tptp.mll)
• Bug 2: CCOption.get_exn in Zipperposition Unif.ml on polymorphic THF
• Bug 3: TSTPSkipSource crash in E prover ccl_clauses.c (fixed upstream)

See README.md for details.