release: finalize CancerPPIr v1.2.0 and strengthen end-to-end validation

[Danil-V-Silin]

Changes

• Finalize scientific interpretation, methodological limitations, and v1.2.0 release documentation.
• Strengthen canonical output schemas, provenance, and deterministic STRING mapping.
• Correct enrichment-mode reporting in the analytical workbook.
• Add synthetic end-to-end integration and smoke validation without running clinical cases.
• Update historical log validation for timestamped pipeline output.

Verification

• Complete repository quality checks: PASSED.
• Complete unit and integration test suite: PASSED.
• All seven curated input files: PASSED.
• Synthetic end-to-end analysis and all 14 output checks: PASSED.
• Git whitespace validation: PASSED.