feat(examples): move form recipes off r.control onto defaults (#144)

[timkindberg]

Summary

Closes #144 (child of #141). Stacks on #149.

Recipes were injecting via r.control, which is a winning intercept, so a path Extra dropped error wiring. Native / RHF / TanStack (and App_09/11/13) now pass defaults to useFormTree({ defaults }).

injectFieldErrors wraps the previous nativeDefaults.field.root so we don't infinite-loop <Default />. Form-lib wiring lives on defaults.field.control with a kind switch. Proof test: path Extra keeps aria-invalid.

Agent did the grind.

Test plan

• Recipes no longer call useRenderNodeRules / r.control
• Path intercept Extra on a field still shows recipe errors + a11y
• Parity matrix still green (native / RHF / TanStack × JSON Schema / Zod)
• CI green

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