ci-cd: parallel tests, docs deployment preview and release

[cusma]

This PR improves docs CI/CD:

1. Shards SC tests scoped by directory (addresses feat: parallelize tests #223);
2. Deploys docs on release (addresses fix: disable docs deployment on main-release sync #286);
3. Deploys docs preview on docs-related PRs;
4. Updates mdbook version.

[Copilot]

Pull Request Overview

This PR enhances the documentation CI/CD pipeline by adding automated deployment on releases and PR preview functionality, while also updating the mdbook version to 0.4.52.

Key Changes:

• Implements docs deployment triggered by successful mainnet releases via workflow_run
• Adds PR preview deployment for docs-related changes with path filtering
• Updates mdbook from version 0.4.43 to 0.4.52 across all workflows

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
.github/workflows/docs-ci.yaml	Adds GitHub Pages preview deployment for PRs, includes path filters for docs-related files, and configures concurrency management
.github/workflows/docs-cd.yaml	Changes trigger from push to workflow_run based on release workflow completion, updates mdbook version, and adds conditional execution
.github/actions/docs-ci/action.yaml	Updates markdown file glob patterns to include SECURITY.md and use recursive pattern, updates mdbook version

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull Request Overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.