Add Promptfoo (LLM eval & red-teaming) parser

[Dashtid]

Description

Adds a parser for promptfoo, an open-source LLM evaluation and red-teaming tool, aligned with the AI-testing direction in discussion #13242.

The parser ingests the JSON results file written by promptfoo eval -o results.json (and promptfoo redteam run -o results.json). promptfoo's pass/fail semantics are inverted relative to most scanners, which is the central design point:

• A result with success: true means every assertion passed — for a red-team probe that means the target model defended the attack — so it is not a finding.
• A result with success: false is a failed assertion (for a red-team probe, the attack succeeded) and becomes a Finding.
• Results with failureReason == 2 (a provider/eval error rather than an assertion failure) are skipped — the test could not run, so it is not a vulnerability.

Other decisions:

• Severity comes from the red-team metadata.severity (critical/high/medium/low). A plain promptfoo eval failure carries no severity metadata and defaults to Medium.
• CWE is mapped from the plugin / harm category as a deliberately coarse starter, verified against MITRE: SQL-injection -> CWE-89, shell/command-injection -> CWE-78, prompt-injection / prompt-extraction -> CWE-1427, PII / privacy -> CWE-200, default -> CWE-1426 (Improper Validation of Generative AI Output).
• Failures for the same plugin against the same target are aggregated into one Finding (nb_occurences, keeping the most severe rung).
• Registered for hash_code deduplication on title + component_name. severity and description are intentionally excluded: description holds the per-run attack input/output, and severity is an aggregate that shifts as the set of failed attempts changes — neither is stable enough for the dedup hash.

Test results

Adds unittests/tools/test_promptfoo_parser.py (14 tests) covering: zero/one/many findings, the severity matrix, the CWE mapping (including the specific *-injection rules taking precedence over the broad rule), aggregation, the plain-eval fallback (severity/title/identity from the failed assertion, metric-over-type), skipping passed and errored results, the lenient input shapes (bare list, top-level results list), shareableUrl -> references, string-form providers, bytes + UTF-8 BOM + non-ASCII input, and rejection of non-JSON input.

The sample scan files under unittests/scans/promptfoo/ are real promptfoo v3 output (results.version == 3).

Documentation

Adds docs/content/supported_tools/parsers/file/promptfoo.md.

Checklist

• Submitted against dev
• Ruff-compliant (ruff.toml, ruff 0.15.16)
• Python 3.13 compliant
• Documentation included
• No model changes (no migration needed)
• Unit tests added
• Labels (for maintainers): suggest Import Scans and settings_changes (touches settings.dist.py for deduplication)

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