feat: add AVE-2026-00083, Silent Guardrail Comparison Failure

[chaksaray]

Summary

• Adds AVE-2026-00083: a protection mechanism (guardrail, approval gate, or judge) that executes on every request and reports a permissive result because its own comparison, branch, or aggregation logic never evaluates the real input — distinct from a missing or bypassed check.
• Grounded in five independently reproduced, executable structural forms against real shipped code (confident-ai/deepeval, openai/openai-agents-python, BerriAI/litellm, guardrails-ai/guardrails, microsoft/autogen, plus AutoGPT classic and archived protectai/rebuff, both with no live disclosure channel) and prevalence data with stated limitations, all from arian-gogani's failopen — proposed in CWE-CAPEC/AI-Working-Group#1. researcher credits him directly; this is his original measurement, not AVE's cataloguing.
• ave_id confirmed via New record: silent guardrail comparison failure #276, including field-by-field distinctness checks against the nearest neighbors: AVE-2026-00063 (check disabled via a legible config flag, versus this record's check that runs and is structurally blind), AVE-2026-00076 (classifier genuinely evaluates real input but is steered, versus this record's comparison that never reaches its deny branch regardless of input), AVE-2026-00078/AVE-2026-00079 (no verification step exists at all, versus this record's check that exists and is invoked), and AVE-2026-00038 (no gating mechanism present at all).
• Note for reviewers: the originating issue thread's own early comment cited "nine across 22 projects" for prevalence — that was the source repository's own earlier, smaller snapshot. The record uses the current, superseding figures from the repo's MEASUREMENT.md (fifteen across thirty-six projects, twenty-one read clean), confirmed by reading the primary source directly rather than the issue summary.
• Scored AIVSS 6.3 (MEDIUM) honestly against the real AARF factors (cvss_base 8.7, aars 4.0) rather than the class's more severe-sounding plain-English framing — reasoning for every factor, and for the owasp_mcp mapping (MCP07, an honestly-imperfect best fit) and the empty owasp_asi/mitre_atlas/nist_ai_rmf fields (each checked against its live primary source directly), is in aivss.notes.
• README (badge, Stats table, collapsible record index, and the "Independent validation" count) and CHANGELOG.md updated per the standard process.

Test plan

• python3 scripts/validate_records.py — all 82 records (80 on develop + this one + an unrelated pending draft already in the working tree) valid against schema/ave-record-1.1.0.schema.json
• python3 scripts/check_fixtures.py — positive and negative fixtures present for AVE-2026-00083
• python3 scripts/write_verification_basis.py — derived verification_basis matches the stamped value, no mismatch
• pytest tests/ -x -q — 478 passed
• Verified every cited GitHub issue/PR URL resolves (200) before including it as a reference