security(attestation): normalize sealed evidence post-open I/O failures #2323

Finding

scripts/ci/verify_scientific_validation_evidence.py::_read_evidence_once() normalized the initial os.open() failure to EvidenceError, but post-open os.fstat() / buffered read() failures could still escape as raw OSError.

This is the verifier-side analogue of #2322. main() catches EvidenceError only, so a storage or descriptor I/O fault after the sealed evidence inode has been opened could bypass the deterministic scientific-validation rejection boundary and produce a traceback/platform-dependent failure instead of a typed invalid-evidence result.

The finding is owner-local: it concerns inert evidence intake before scientific semantics are evaluated. TEPP must not copy the mutable implementation.

Acceptance

• Add a source-level hostile RED that opens a real regular evidence file and injects an OSError during the post-open read path.
• _read_evidence_once() must normalize post-open metadata/read OSError to a deterministic EvidenceError that identifies evidence intake failure.
• Preserve deliberate EvidenceError outcomes such as non-regular-file refusal rather than swallowing them in a broad catch.
• Preserve one-open O_NOFOLLOW | O_NONBLOCK, descriptor-relative pinned-root reads, 16 MiB+1 bound, and exact-byte hash/semantic use.
• Keep the path inside the existing Scientific Validation Evidence Quality 100% owned branch-coverage/interrogate/compileall denominator; no skip/xfail or denominator rewriting.
• Do not merge or claim hosted GREEN until the exact repaired head settles normally.

Repair lineage

• Source-level RED: 475b6bd83a016d45131f7f49434038c93ac3f926.
• Causal production repair: e630dc6bc2d42c9aa69fad60667121def6314d8c.
• CHANGELOG: c1454588a5b32305f2395806b990fe7f91ec7614.
• Doctoring: e725382f74323f0ebee79028ac739db5d906d7f1.
• Quality path authority: 91dc1849efb5ca9e98118056d96acf401166692b.

Current exact head 91dc1849efb5ca9e98118056d96acf401166692b is still non-terminal. Scientific Validation Evidence Quality run 35571062142 / job 106242616064 is queued with no assigned runner and no steps, so no hosted GREEN or hosted failing RED is claimed.

Refs #2299 #2300 #2322 #2164 #712 ContextualWisdomLab/TEPP#637.