Address code review feedback: remove backup file, fix lint errors, add documentation

[Copilot]

Addresses code review feedback from PR #94 regarding test code quality, unused imports, and missing documentation.

Changes

• Removed backup file: Deleted maya_date_correlations.json.bak from version control
• Fixed lint errors: Replaced chai assertions (to.be.true, to.be.null) with standard forms (to.equal(true), to.not.equal(null)) to avoid ESLint warnings
• Removed unused imports: Cleaned up findCorrelation imports in full-date.spec.ts and western.spec.ts
• Fixed TypeScript errors: Changed eventGroups: { [event: string]: any[] } to Record<string, CorrelationData[]>
• Added documentation: Documented winal radix correction purpose in test file:

/**
 * The winal radix correction refers to how 20‑day winals are handled when mapping
 * Long Count positions to a fixed day count (JDN) and then to Gregorian/Julian
 * calendar dates. Historically, small off‑by‑one errors in this radix handling
 * can shift whole correlation constants by one or more days.
 */

All tests passing. No security issues detected.

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Note

Cleans up test suite and documentation while removing an accidental backup file.

• Deletes backup dataset src/__tests__/maya_date_correlations.json.bak
• Replaces Chai assertions (to.be.true, to.be.null, etc.) with ESLint-friendly forms (to.equal(true), to.not.equal(null)) across specs
• Tightens types (e.g., eventGroups to Record<string, CorrelationData[]>) and removes unused findCorrelation imports in full-date.spec.ts and western.spec.ts
• Adds documentation in correlation-validation.spec.ts explaining the "winal radix correction" and its relevance to correlation constant validation
• No behavioral changes to core logic; tests remain green

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