feat(exact): report determinant scale overflow precisely

[acgetchell]

• Add a typed LaError::DeterminantScaleOverflow path for exact determinant scale exponent failures
• Convert det_exact_f64 directly from the shared Bareiss integer/exponent pair while preserving Overflow for finite-f64 conversion failures
• Reuse vector finiteness scanning across raw and proof-bearing constructors
• Harden docs version sync checks for reordered inline-table dependency snippets and pruned Markdown traversal

Closes #139

Summary by CodeRabbit

• New Features

  • Added explicit error for determinant scaling overflow and improved exact→f64 determinant conversion.

• Bug Fixes

  • More reliable detection of stale dependency snippets in documentation checks (handles inline-table forms and reordered keys).

• Documentation

  • Expanded Matrix guidance and added an [Unreleased] changelog section with version-sync notes.

• Tests

  • Broadened tests for exact determinant behavior with mixed-scale values and added a test for reordered inline-table keys.

[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: bf9807a0-b934-468b-bb31-c3f994fc5839

📥 Commits

Reviewing files that changed from the base of the PR and between 928f62b and 532093a.

📒 Files selected for processing (1)

• src/exact.rs

🚧 Files skipped from review as they are similar to previous changes (1)

• src/exact.rs

---

📝 Walkthrough

Walkthrough

Refactors exact determinant→f64 conversion to use a direct bigint+exponent helper and adds DeterminantScaleOverflow; centralizes vector finiteness scanning; removes redundant LU/LDLT tolerance tests; and improves docs-version-sync script, tests, and CHANGELOG entries.

Changes

Exact Determinant Scaling and Error Handling

Layer / File(s)	Summary
DeterminantScaleOverflow error variant definition src/lib.rs	LaError::DeterminantScaleOverflow enum variant with dim and min_exponent, a const fn constructor, Display formatting, and a unit test for the message.
Exact determinant f64 conversion and error handling src/exact.rs, src/lib.rs	Adds bigint_exp_to_finite_f64 to convert (BigInt, exp) → f64 without materializing BigRational, introduces determinant_scale_exp for checked D*e_min scaling returning DeterminantScaleOverflow, updates bareiss_det_int_finite and FiniteMatrix::det_exact_f64, and revises determinant docs to include the new error.
Mixed-scale determinant property tests tests/proptest_exact.rs	Adds mixed_scale_finite_f64 strategy and gen_mixed_scale_diagonal_exact_det_proptests! (D=2..=5) verifying det_exact, det_sign_exact, and det_exact_f64 against BigRational expectations and overflow/non-finite cases.

Vector Finiteness Centralization

Layer / File(s)	Summary
Shared finiteness scanning helper and refactoring src/vector.rs	Adds internal first_non_finite_entry_in that scans entries and returns the first non-finite index; FiniteVector::new and Vector::try_new now use this helper for consistent LaError::non_finite_at behavior.
Tolerance test cleanup src/ldlt.rs, src/lu.rs	Removes redundant invalid_tolerance_rejected tests from both factorization test modules.

Documentation Sync Tooling and Changelog

Layer / File(s)	Summary
Docs version sync script improvements scripts/check_docs_version_sync.py	Adds os.walk-based markdown discovery with SKIP_DIRS filtering and broadens the dependency-snippet regex to match quoted and inline-table forms with arbitrary key ordering.
Docs version sync test coverage scripts/tests/test_check_docs_version_sync.py	Adds from __future__ import annotations, Path type hints for tmp_path, updates test signatures, and adds a test for reordered inline-table keys producing a stale-snippet mismatch.
Changelog and module documentation updates CHANGELOG.md, src/matrix.rs	Adds an [Unreleased] section and compare link, updates a [0.4.2] bullet, and expands Matrix module docs describing fixed-size/stack allocation guidance and links to other crates.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• acgetchell/la-stack#140: Directly refines the docs-version sync tooling and tests (file-walking logic and regex patterns).
• perf: integer-only Bareiss determinant via BigInt (#64) #73: Related changes in src/exact.rs affecting the Bareiss determinant pipeline and det→f64 handling.
• refactor(invariants): simplify finite proof wrappers #134: Overlaps with centralizing vector finiteness construction in src/vector.rs.

Suggested labels

documentation, enhancement, rust, testing, api

"🐰
I hopped through integers, exponents, and docs so neat,
No BigRational bloomed — a slimmer f64 to meet.
One helper finds the first non-finite spot,
Tests and changelogs tidy, regexes catch the lot.
A little rabbit clap for code that's neat and fleet."

🚥 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 PR title "feat(exact): report determinant scale overflow precisely" directly reflects the main objective of adding typed DeterminantScaleOverflow error handling for exact determinant calculations, matching the changeset focus.
Linked Issues check	✅ Passed	The PR successfully addresses all coding requirements from #139: removes redundant tolerance tests in LU/LDLT, consolidates vector finiteness scanning via first_non_finite_entry_in helper, preserves public APIs, and adds DeterminantScaleOverflow error variant.
Out of Scope Changes check	✅ Passed	All changes are scoped to #139 objectives: determinant scale overflow handling, vector finiteness consolidation, test removal/addition, and documentation improvements. Documentation updates to CHANGELOG, matrix module, and docs version sync are supporting changes.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

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🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/139-exact-det-scale-overflow

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[codecov]

Codecov Report

❌ Patch coverage is 96.36364% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 99.61%. Comparing base (90a4200) to head (532093a).

Files with missing lines	Patch %	Lines
src/exact.rs	95.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #141      +/-   ##
==========================================
+ Coverage   99.47%   99.61%   +0.14%     
==========================================
  Files           5        5              
  Lines        2838     2846       +8     
==========================================
+ Hits         2823     2835      +12     
+ Misses         15       11       -4     

Flag	Coverage Δ
unittests	99.61% <96.36%> (+0.14%)	⬆️

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