[orm #7] Docs: move ORM from candidate to shipped

[suleimansh]

Part of #64. Depends on #orm-2/#orm-3.

Update Architecture.md (ORM/schema candidate -> shipped, end-state ai-sdk + orm + schema), the root README package table, and the docs site (guide + per-package pages).

Acceptance: docs reflect the graduated data layer; no 'candidate' language left.

[suleimansh]

Drafted in #73 (HOLD until publish + #66). Full sweep: README table + diagram, docs/packages + guide indexes, vitepress sidebar (new data-family group), Architecture.md candidate->graduated, and new orm.md + schema.md pages. vitepress build passes. Schema documented as preview. Merge only after the @gemstack naming is confirmed (#66) and the packages publish (#67/#68), since the docs site auto-deploys on merge.

[suleimansh]

Hold + rework per #66: the data family will not be presented as GemStack packages. Rework the docs (and draft PR #73) to document the data layer under @universal-orm, separate from the GemStack umbrella.

[suleimansh]

Moot per #66: the ORM is not a GemStack package, so there is nothing to move from candidate to shipped here. Data-layer docs live with @universal-orm in vike-data.