docs: documentation and standards guides for all toolkit modules

[kristopherjturner]

Overview

Write comprehensive documentation covering the toolkit's purpose, all modules, integration guides for solution repos, and standards guides for naming conventions, tagging, and pipeline patterns.

Scope

• docs/index.md — Toolkit overview and getting started
• docs/configuration/ — Variable registry reference, schema documentation
• docs/deployment/ — Integration guide for consuming repos (PowerShell + Python)
• docs/standards/ — Naming conventions, tagging policies, pipeline template usage
• docs/roadmap.md — Toolkit maturity roadmap and future features
• docs/contributing.md — How to add new variables, update standards, submit PRs

Acceptance Criteria

• Integration guide enables a new repo to consume the variable registry in <30 minutes
• All registry variables documented with type, description, and example
• Naming convention and tagging standards fully documented
• Pipeline template usage documented with copy-paste examples
• Docs site builds without warnings

Dependencies

• Parent Epic: [Epic] Azure Local Toolkit Platform Automation Full Build-Out #9
• Variable registry: feat: variable registry implementation (shared config for all solution repos) #10
• Standards replication: feat: standards replication mechanism across all solution repos #11

Priority Note

Priority/medium — documentation deferred until core modules stabilize.