📖 docs: clarify partial credit logic for Branch-Protection tiers

[aban-alazzeh]

What kind of change does this PR introduce?

Docs update 📖

• PR title follows the guidelines defined in our pull request documentation

What is the current behavior?

The documentation for the Branch-Protection check states that "Each tier must be fully satisfied to achieve points at the next tier." This implies an all or nothing scoring model for each tier, leading users to believe they will receive zero points for a tier if even one requirement is missed

What is the new behavior (if this is a feature change)?**

This PR updates the documentation to accurately reflect the implementation logic in checks/evaluation/branch_protection.go. The updated wording clarifies that while tier progression is strict (you cannot earn points for Tier N+1 until Tier N is complete), users do receive partial credit for each requirement met within their current active tier via the normalizeScore function.

• Tests for the changes have been added (for bug fixes/features)

Which issue(s) this PR fixes

Fixes #5009

Special notes for your reviewer

I’ve updated docs/checks/internal/checks.yaml and ran the generation script to refresh docs/checks.md. This change makes the "partial credit" logic in normalizeScore more transparent, so users can clearly see how it works.

Does this PR introduce a user-facing change?

NONE