FR-029 — Metadata API + runtime-metadata-driven UI (backend-agnostic)

[dmealing]

Metadata endpoint per backend + browser runtime loader + runtime grid/forms + both-ways (codegen vs runtime) demo + 5-backend verification. See gap doc Theme 1.

Spec / design: https://github.com/metaobjectsdev/metaobjects/blob/main/docs/superpowers/specs/2026-06-13-metadata-runtime-ui-and-serializers-gaps.md
Target release: 1.4

Tracked in spec/roadmap.md (FR registry). Status lives here; the roadmap is the source of truth.

[dmealing]

Status note (audit 2026-07-02): the runtime-driven grid column/config builder slice already shipped — buildGrid() in client/web/packages/runtime-web/src/grid-from-metadata.ts (PR #40, ea2b9e93) with tests. The wire format this FR needs is also already frozen: the canonical metadata JSON serializer ships byte-identically in all 5 ports, so the metadata API is "HTTP-expose the existing canonical output." Remaining (post-1.0, target 1.4): the /_meta endpoint per backend, the browser metadata loader in runtime-web, runtime-driven forms, and the 5-backend demo. Keeping open.