[#7019] Add visual diagrams to matching-model-explanation.md

[Aitem]

Summary

• Added 4 Mermaid diagrams to docs/modules/mdm/matching-model-explanation.md as requested in HealthSamurai/sansara#7019
• Matching Score Calculation Flow — flowchart showing Record A vs Record B → feature comparison → weight accumulation → threshold check → decision
• Blocking Mechanism — diagram illustrating how blocking keys (name, DOB, address) reduce N×N comparisons to filtered candidate pairs
• Feature Weight Impact — step-by-step waterfall showing cumulative score: +13.34 (fn) → +10.59 (dob) → −10.52 (ext) → +1.85 (sex) = 15.26 total
• Threshold Decision Boundaries — color-coded block diagram (Non-match / Manual Review / Auto-merge) plus examples table with 4 scenarios

All diagrams follow the Mermaid style already used in merging-and-unmerging-records-usdmerge-and-usdunmerge.md.

References

• Parent issue: HealthSamurai/sansara#7018 (MPI Illustrations - model tuning guide)
• Task issue: HealthSamurai/sansara#7019

Test plan

• Verify Mermaid diagrams render correctly in GitBook
• Check color-coded styles display properly (green/yellow/red)
• Validate example score calculations in the table are mathematically correct
• Confirm diagrams reference the same model values as the JSON example on the page

🤖 Generated with Claude Code

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Note

Low Risk
Documentation-only change that adds Mermaid diagrams and an examples table; main risk is rendering/formatting issues in the docs pipeline rather than runtime behavior.

Overview
Enhances docs/modules/mdm/matching-model-explanation.md with four Mermaid diagrams illustrating the matching score flow, blocking/candidate-pair reduction, and how feature weights accumulate into a total score.

Adds a threshold decision diagram plus a small examples table showing how sample feature weights map to Auto-merge / Manual Review / Non-match outcomes.

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