Function contentDraftFallback

Whether a watched content doc's reactive read may fall back to the DRAFT — the fallback half of the per-doc resolution rule contentReleaseName starts. Mirrors the engine's own hydration under the instance's effective perspective (instance.perspective ?? DEFAULT_CONTENT_PERSPECTIVE): a draft is visible only when that perspective names 'drafts' — the drafts default, 'drafts' itself, or a stack like [release, 'drafts']. Under 'published' / 'raw' and under a stack without a 'drafts' entry ([release], ['published']) drafts are invisible, and an adapter feeding one would evaluate content the engine's read can never see.

Raw refs (readsRaw) answer true by contract, and it is load-bearing: instance / ancestor / system.release docs have no draft form, and the true keeps them on the adapters' raw per-doc read path — never a perspective-scoped content read.