Update authoring docs after legacy Model removal

Remove or rewrite documentation that references the legacy Model class, decorators, and createSchema. After this work, the authoring docs present createContentModelSchema as the single path.

Files to update

site/content/docs/authoring/model-api.md — Delete entirely (full Model API reference, no longer applicable)
site/content/docs/authoring/overview.md — Remove references to Model class and decorator approach
site/content/docs/authoring/patterns.md — Rewrite patterns to use createContentModelSchema exclusively
site/content/docs/authoring/content-models.md — Review for any legacy cross-references
site/content/docs/packages/authoring.md — Ensure community package guide only references the modern API

Acceptance Criteria

model-api.md is deleted
No remaining references to Model, @attribute, @group, @groupList, @id, or createSchema in any authoring doc
patterns.md examples all use createContentModelSchema
overview.md presents createContentModelSchema as the sole schema API
Community package authoring guide uses only the modern pattern
Site builds successfully (cd site && npm run build)
No broken internal links (removed page references updated)

Dependencies

WORK-103 (legacy code removed — docs should match the actual API)

References

SPEC-032 (parent spec)

Resolution

Completed: 2026-04-02

Branch: claude/implement-spec-032-2KBbw

What was done

Deleted model-api.md (full Model API reference page)
Removed model-api from nav in _layout.md
Rewrote Hint example in authoring-overview.md to use createContentModelSchema
Updated checklist tables to reference createContentModelSchema instead of "Model class"
Rewrote patterns.md — header+body split, child item runes, and field ordering sections
Updated content-models.md — removed Model class cross-reference, updated base comment
Rewrote packages/authoring.md — game-item example uses createContentModelSchema
Site builds successfully (128 pages)