fix(rasch-cml): harden native dispatch controls

[seonghobae]

Scope

Fix #905 at the public Rasch CML/Andersen LR validation boundary without changing psychometric computation.

Test-first lineage

• RED 906d62edad1e0efe992381b05ad10c4587cb16a9 requires malformed responses/groups and hostile scalar subclasses to fail before compiled-core discovery or coercion callbacks, while genuine NumPy controls still reach the native-dispatch boundary.
• GREEN 75a52d536a3bee6b191dd078b4909aaaa58a4455 adds exact-type iteration/tolerance admission, bounds iteration work with the repository cap, validates all public inputs before _core_module(), and passes only trusted built-in scalars into PyO3.
• 5d72dc72557c04ffe4eb7783bc19e5d05dc5cb0e records release evidence.

Preserved boundary

• Rasch conditional likelihood, CML estimation, information/SE, Andersen LR statistic, degrees of freedom, p-value, retained-person accounting, and all result-affecting arithmetic remain Rust-owned and unchanged.
• Existing binary response and group-label semantics remain unchanged.
• Exact built-in and genuine supported NumPy integer/floating scalar controls remain supported; booleans/subclasses/arbitrary coercion providers fail before callbacks.
• Valid requests still fail with the established RuntimeError when the compiled Rust core is unavailable.
• No Python numerical fallback, dependency, provider, persistence, workflow, package-version, gate, or downstream-ownership change.

Lifecycle discipline

The source is Ready for review. Integration remains contingent on live exact-head CI/security/package/provenance evidence, zero operative unresolved review findings, and the repository's required independent non-author approval. Protected base, source head, reviews, threads, and checks must be refetched immediately before any integration action; predecessor evidence does not transfer.

Fixes #905.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: b04e16ae-971f-41ae-8dc3-bd77f4f29fea

📥 Commits

Reviewing files that changed from the base of the PR and between fb67ced and 5d72dc7.

📒 Files selected for processing (3)

• docs/changelog.d/905-rasch-cml-control-boundary.md
• python/fast_mlsirm/rasch_cml.py
• tests/test_rasch_cml_native_boundary.py

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📝 Walkthrough

Walkthrough

Rasch CML and Andersen LR now validate input data and scalar controls before compiled-core discovery. The wrappers reject hostile coercion objects, accept supported NumPy scalars, enforce bounds, and add regression tests for validation order and native dispatch.

Changes

Rasch CML control boundary

Layer / File(s)	Summary
Strict scalar validation python/fast_mlsirm/rasch_cml.py	The module recognizes supported NumPy scalar types and validates iteration limits and tolerances without invoking caller-defined coercion.
Validated native dispatch and regression coverage python/fast_mlsirm/rasch_cml.py, tests/test_rasch_cml_native_boundary.py, docs/changelog.d/905-rasch-cml-control-boundary.md	fit_rasch_cml and andersen_lr_test validate controls before Rust-core loading. Tests cover malformed inputs, hostile scalar subclasses, valid NumPy scalars, and loader behavior. The changelog records the boundary changes.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to 5d72d

The change hardens validation for Rasch CML and Andersen LR controls while preserving existing computations and supported inputs; no actionable merge-blocking risk remains beyond normal checks and review.

Possibly related issues

• Reject executable equating control providers before Rust dispatch #897 — Both issues harden Python trust-boundary validation before Rust-core discovery, although they target different APIs.

Possibly related PRs

• ContextualWisdomLab/fast-mlsirm#847 — Both changes reject hostile scalar coercion before native-core loading.
• ContextualWisdomLab/fast-mlsirm#869 — Both changes preserve genuine NumPy scalar support while hardening integer validation.
• ContextualWisdomLab/fast-mlsirm#888 — Both changes prevent caller-controlled numeric coercion during native dispatch.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The changes satisfy issue #905 by validating inputs and controls before native discovery while preserving computation and adding regression coverage.
Out of Scope Changes check	✅ Passed	The code, tests, and changelog changes directly support the validation-hardening objectives in issue #905.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: hardening Rasch CML native dispatch controls.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/rasch-cml-control-boundary-905

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