test: verify state isolation for longestCommonSubsequence (Issue #25) - #63

Description
Verified external state isolation and idempotency for longestCommonSubsequence in Dynamic-Programming/LongestCommonSubsequence.js, and created the required check runner script.

Related Issue
Fixes: #25

Type of Change

• Bug Fix
• New Feature
• UI/UX Improvement
• Performance Improvement
• Tests
• Documentation
• Refactoring / Maintenance
• CI/CD

Changes Made

• Evaluated observable dependencies (determined to be a pure function with no external dependencies).
• Tested smallest valid input ("", "") and ordinary input ("ABCDGH", "AEDFHR"), referencing precondition source line 30 of Dynamic-Programming/LongestCommonSubsequence.js.
• Added state isolation and idempotency tests in Dynamic-Programming/tests/LongestCommonSubsequence.test.js asserting that repeated calls after intervening inputs return identical results.
• Created work/R50-T025/check.py to execute tests in non-watch mode and record versions and logs.

Screenshots / Recordings
N/A

Testing

• Executed python3 work/R50-T025/check.py locally.
• Verified test suite passes for Dynamic-Programming/tests/LongestCommonSubsequence.test.js.

Checklist

• I have tested my changes locally.
• I have added or updated tests, if needed.
• I have updated documentation, if needed.
• I have followed the project's coding guidelines.
• I have run the relevant tests and checks.
• I have addressed previous review feedback, if applicable.

Additional Notes
N/A