Replace in-repo .md cross-references in skill content with Microsoft Learn URLs

Start by auditing skills/**/*.md and the mapping from PR #14, including the unresolved monitoring and inline-text questions. Use the listed Learn references to identify every in-repo .md link, then run scripts/validate-skills.ps1. Done means all applicable skill links resolve to canonical Learn URLs and the validator passes.

Problem

Skill rule files cross-reference each other and adjacent skills using relative .md paths (e.g. [security-private-endpoint](security-private-endpoint.md), [ha-cross-region-replica](../high-availability/ha-cross-region-replica.md)). When the skill content is consumed by an agent or rendered outside the repo, these in-repo links don't resolve — the consumer needs links to the official Microsoft Learn articles instead.

Proposed fix

Replace every *.md link inside skill content (rule files and SKILL.md) with the canonical Learn URL. Each rule already lists its primary Learn source in its ## References section, so the mapping is straightforward.

Mapping (from PR #14 audit)

Sibling rules — skills/security/

Cross-skill references

Open questions

1. Four security rules collapse to the same RBAC Learn article (how-to-connect-role-based-access-control) — security-entra-rbac, security-database-roles, security-azure-rbac-actions, security-token-lifetime-revocation. That single Learn article is the source for all four. Acceptable, or do we want sub-section anchors?
2. Two rules collapse to azure/documentdb/security — security-tls-required and security-admin-password-and-identity-separation. Both pulled from the "Secure your cluster" overview.
3. Monitoring landing page — confirm the right canonical URL for the ../monitoring/ directory reference.
4. Inline non-link text like `storage/` in SKILL.md (parenthetical "Premium SSD v1 only — see storage/") — convert to Learn link too, or leave as in-repo navigation hint?

Scope

This issue is about all skill folders, not just security/. PR #14 surfaced the issue but the same pattern almost certainly exists in high-availability/, storage/, and any future skill. Recommend a one-pass sweep across skills/**/*.md once the open questions are resolved.

Suggested implementation

A small PowerShell or Python script that walks skills/**/*.md, applies the mapping table above, and reports any unmapped .md) link for manual review. Validator (scripts/validate-skills.ps1) should pass after the sweep.

Originating context

Surfaced during review of PR #14 (docs/security-rbac). Mapping table was generated by auditing the ## References section of each affected rule file.