Docs/add docs ci : add mkdocs build + link-check workflow

[ibloud]

builds docs with mkdocs and runs a link-checker (no deployment in this PR).
issue link: #5

[ibloud]

Thanks — initial review checklist for this documentation PR:

• Title & scope

  • PR title accurately summarizes changes and is scoped to docs only.
  • PR body includes provenance statements for any literary/philosophical material (see PUBLIC_DOMAIN_DESIGN.md).

• Licensing & IP

  • Confirm no proprietary/copyrighted text or art was added (check PUBLIC_DOMAIN_DESIGN.md guidance).
  • Confirm that the Daddy's Little Mortis commercial IP boundaries are preserved and contributors are aware of the CC BY-NC-SA 4.0 constraints.

• Architecture verification

  • Verify the pipeline hook points described in docs/ARCHITECTURE_OVERVIEW.md match intended Unity/Unreal component lifecycle events (OnValidateIntent, OnApplyMove, OnResolveCapture).
  • Confirm the GhostPiece component blueprint can be implemented as a serializable component in our chosen engine (Unity: ScriptableObjects/Components; Unreal: ActorComponents/Blueprints).

• Consistency & cross-links

  • docs/* link back to README.md and vice versa (add anchor links if helpful).
  • Rulebook dimensions (14x14 cross topology) and any canonical board diagrams are referenced and consistent.

• Tests & tooling

  • Identify which code paths need basic unit tests (MovementEngine, ScoringEngine) and add placeholders/issues for those tests.
  • Confirm determinism & replay verification steps listed are implementable with existing simulation snapshots.

• Contributor safety & provenance

  • Confirm the PUBLIC_DOMAIN_DESIGN instructions are sufficient and add a one-line PR checklist item for future PRs that add literary/art references: “I confirm this material is public-domain or original — provenance: ”.

• Docs quality

  • Spelling/grammar scan
  • Add at least one small diagram or SVG for Rules.md (placeholder OK)
  • Quickstart contains accurate run instructions or a clear note that the build is not currently runnable.

• Merge readiness

  • Maintainer sign-off from: systems engineer (architecture), lead designer (game rules), legal/reviewer (public domain verification).

[ibloud]

Added ENGINE_ACCESSIBILITY_AUDIO_AURA.md to formalize non-visual signaling for Radius of Ruin/Veiled/Sanctuary, and cross-linked it with existing accessibility/grant docs; this is docs-only and intended to preserve accessibility behavior across future audio/status/mix changes.