fix(ci): pin grm-recovery rust toolchain and align metadata scalar test

[seonghobae]

Problem

Both python (3.12) and python (3.14) CI jobs are currently red on main itself (reproduced independently of any in-flight PR's diff, via a disposable worktree at main@bc0377a), with two unrelated contract-test regressions:

FAILED tests/test_rust_toolchain_contract.py::test_every_product_and_statistical_rust_action_uses_1_97_1 - AssertionError: assert 5 == 4
FAILED tests/test_scoring_contract_metadata.py::test_metadata_rejects_string_subclasses_before_callbacks - Failed: DID NOT RAISE ValueError

Fix 1: missing Rust toolchain pin

#1012 added the grm-recovery job to .github/workflows/statistical-studies.yml with a bare dtolnay/rust-toolchain@... step — no with: toolchain: 1.97.1, unlike every sibling step in this file and ci.yml. test_rust_toolchain_contract.py's own docstring states its purpose exactly: "No Rust-backed verification lane may silently float to a new stable release." It correctly caught this.

• Added the missing with: toolchain: 1.97.1 pin to grm-recovery.
• Updated the test's hardcoded expected_counts for statistical-studies.yml from 4 to 5, since the fifth, now-correctly-pinned job is a legitimate addition, not a regression to revert.

Fix 2: stale test expectation after an intentional behavior change

#992 introduced _normalize_metadata_scalar in python/fast_mlsirm/scoring/_contract_safety.py, which safely accepts str/int/float subclasses by copying their value through the inert base-type descriptor (str.__str__, int.__int__, float.__float__) without ever invoking a subclass-defined method — the same safe-normalization pattern already used elsewhere in this PR's own hardening pass. That PR did not touch tests/test_scoring_contract_metadata.py, so the pre-existing test_metadata_rejects_string_subclasses_before_callbacks (written under the prior, stricter "reject subclasses outright" regime) kept asserting a ValueError that the new, intentional implementation no longer raises.

Verified via git show that _normalize_metadata_scalar's only code path for a str subclass is return True, str.__str__(value) (safe acceptance) — there is no branch that would raise for this input, confirming the test's expectation was stale rather than the implementation being a regression.

Renamed the test to test_metadata_normalizes_string_subclasses_without_callbacks and updated it to assert the actual, intended contract: the hostile subclass's strip/encode overrides are never invoked (callback_count == 0), and the metadata value is safely normalized to a plain str equal to its content.

Verification

• pytest tests/ (Python 3.12): 5858 passed, 1 skipped, 0 failed.
• python scripts/render_changelog_fragments.py --check CHANGELOG.md: passes with the new fragment.
• git diff --check: clean.
• Workflow YAML re-parsed with yaml.safe_load after the edit: valid.

No statistical, estimator, or public API behavior changed — this is CI-configuration and test-contract alignment only.

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Generated by Claude Code

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Summary by CodeRabbit

• Documentation

  • Expanded the changelog with updates covering validation, provenance, accessibility, reporting, security, model governance, and release processes.
  • Documented the Rust toolchain requirements for scheduled statistical studies.

• Bug Fixes

  • Improved handling of custom string values by safely normalizing them without triggering overridden behavior.

• Reliability

  • Standardized the statistical-study environment on Rust 1.97.1 for more consistent results.

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📝 Walkthrough

Walkthrough

The pull request pins the statistical-study Rust toolchain to 1.97.1, updates the metadata string-subclass contract to normalize safely, adjusts the related test, and adds extensive changelog entries for the 0.8.0 and Unreleased changes.

Changes

Contract and release updates

Layer / File(s)	Summary
Rust toolchain pin .github/workflows/statistical-studies.yml, tests/test_rust_toolchain_contract.py	The grm-recovery job uses Rust 1.97.1. The contract test expects five Rust toolchain actions.
Metadata normalization tests/test_scoring_contract_metadata.py, docs/changelog.d/1300-ci-contract-drift.md	The metadata test verifies callback-free normalization of string subclasses to exact str values. The changelog records the contract.
Release and security changelog CHANGELOG.md	The changelog adds Unreleased, 0.8.0, and Security entries covering conformance, provenance, Rust ownership, validation, accessibility, reporting, and input hardening.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 47340

The PR’s CI pinning and test-contract updates are localized, and no actionable merge-blocking risk remains; the remaining follow-ups are limited to documentation accuracy and optional test hardening.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely summarizes both primary changes: pinning the Rust toolchain and aligning the metadata scalar test.
Docstring Coverage	✅ Passed	Docstring check was indeterminate for this PR — some files could not be analyzed in time. Not blocking.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.

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Actionable comments posted: 2

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Inline comments:
In `@docs/changelog.d/1300-ci-contract-drift.md`:
- Line 6: Update the changelog entry to reference
test_metadata_normalizes_string_subclasses_without_callbacks, or remove the
internal test identifier while preserving the description of string-subclass
normalization without invoking subclass-defined methods.

In `@tests/test_scoring_contract_metadata.py`:
- Around line 98-106: Add a __str__ override to _HostileMetadataText that
increments callback_count and raises, so
test_metadata_normalizes_string_subclasses_without_callbacks detects
normalization via str(value) while preserving the existing strip and encode
protections.

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📥 Commits

Reviewing files that changed from the base of the PR and between 0827dfa and 473405a.

📒 Files selected for processing (5)

• .github/workflows/statistical-studies.yml
• CHANGELOG.md
• docs/changelog.d/1300-ci-contract-drift.md
• tests/test_rust_toolchain_contract.py
• tests/test_scoring_contract_metadata.py

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Devin Review found 3 new potential issues.

[seonghobae]

Current-head Strix check was re-run through the GitHub Actions API for exact head a441ef33b7c77c2c379ec4e222cb3a49ae9a75bf. The failed attempt is provider infrastructure, not a source finding: NVIDIA NIM returned HTTP 429 rate limits, the configured fallback also emitted provider-unavailable output, and the required gate correctly failed closed. All other completed required checks and the current review findings are clean; the rerun remains authoritative.