[Docs] Create VISION.md and vision artifacts for Layer5 Docs

[Zayden369]

Objective

Create a repository-specific VISION.md for layer5io/docs, following the established Layer5 vision-document approach rather than a generic project vision.

Scope and constraints

• Documentation only. Do not change build or product behavior.
• Add VISION.md at the repository root.
• Ground the vision in the actual responsibilities and practices of layer5io/docs.
• Preserve existing documentation conventions and repository guidance.

Quality bar

• Nothing generic. Statements should be specific to the Layer5 documentation repository.
• Every substantive claim should be traceable to this repository, authoritative Layer5/Meshery source repositories, or published Layer5 material.
• Distinguish documented product behavior from aspirational direction.
• Follow the repository's established voice and contribution conventions.
• Preserve compatibility concerns documented in AGENTS.md, including stable URLs/anchors and verification of product behavior against authoritative implementations.
• Use plain hyphens rather than em dashes.
• No AI attribution in repository content.

Proposed deliverables

• VISION.md at the repository root.
• docs/vision/vision-evidence.md - claim-by-claim traceability for the vision.
• docs/vision/vision-hypotheticals.md - calibrated scenarios that clarify what changes align with or conflict with the documentation vision.

Before opening the PR, validate each claim against repository evidence and relevant authoritative Layer5/Meshery sources.