Scaffold the Zeliard 2 Godot project

[nolanvenhola]

What changed

• establishes 7_Zeliard2/Game as the permanent Godot 4.7.2 production project
• separates shipping runtime code from editor-only Zeliard Creator integration
• defines typed GDScript, dependency, diagnostics, testing, and modern-resource conventions
• adds structured runtime logging and the shared ZeliardContent validation foundation
• adds architecture enforcement, headless contract tests, and a main-scene smoke test
• adds Windows and single-threaded Web release exports
• adds path-scoped GitHub Actions CI that installs the pinned engine/templates and runs the same local validation command
• links the sequel production project from the repository README

Validation

• architecture and typed coding rules: PASS (6 scripts)
• production scaffold scenarios: PASS (4 tests)
• Creator EditorPlugin startup: PASS
• main scene smoke: PASS
• Windows release export and executable smoke: PASS
• Web release export: PASS
• workflow YAML parse and staged whitespace checks: PASS

Boundaries

The scaffold contains no original Zeliard assets or legacy resource formats. Domain schemas remain scoped to #240; this PR supplies only their shared validation contract and project infrastructure.

Closes #239