Implement #117 field error-presentation seam: Default errors={ValidationError[]}

[timkindberg]

Question

Land the library half of the seam locked in #117: recipes inject per-field errors via <Default of={field} errors={ValidationError[]} /> (prop, recipe-pre-gated) and reuse FormFrame’s accessible field composition — instead of each recipe rebuilding FieldShell / FieldErrors / a11y.

Play after the merged form-lib recipes (PR #127 / #123+#124). Those recipes prove BYO errors work; they do not yet exercise this inject path (DefaultFieldRoot still reads ValidationProvider / the store).

Recommended model

Sonnet 5 — the interface is locked; this is careful React/renderer surgery + thinning the example recipes onto it. Escalate only if the renderNodeRules / parts re-sourcing gets subtle.

Locked contract (#117 — do not reopen)

• Injected shape: errors: ValidationError[], per field, keyed by node.path, pre-gated by the recipe (present == show). No show flag.
• Mechanism: a prop on ADR-017 re-entry — <Default of={fieldNode} errors={…} />. Not a new context-shaped public seam. renderNodeRules handlers own errors in lexical scope and thread them into parts; any “set once” ergonomic is YAGNI until earned.
• a11y (KEEP): control gets aria-invalid + aria-describedby={fieldErrorId(path)}; error list gets id={fieldErrorId(path)}. No role="alert" by default (today’s DefaultFieldErrors still has it — drop it as part of this work).
• KEEP: default field composition; movable Errors / Control parts re-sourced from the injected errors; ValidationError + groupErrorsByPath; fieldControlId / fieldErrorId.
• Still recipe / later Cleanup: drop validation-* packages, slim useFormTree, finalize ADRs #126: store-backed hooks, ValidationProvider, status hooks, submit-gating — do not re-entrench them. This ticket only adds the inject path and prefers it when errors is passed.

Acceptance

1. Default / field root accepts optional errors?: ValidationError[]. When provided, display + a11y are driven from that prop (not the store). When omitted, current store-backed behavior remains until Cleanup: drop validation-* packages, slim useFormTree, finalize ADRs #126 demotes it (dual path is OK short-term).
2. Library default field errors: no role="alert".
3. Example recipes (fieldPresentation.recipe.tsx + RHF/TanStack controls, or a thin follow-up commit) use the inject path and delete duplicated shell/a11y where the library now covers it — keep only form-lib-specific control wiring + error-shape → ValidationError[] (or message) normalization.
4. Unit/browser tests cover: inject shows errors; a11y attrs track injected errors; omit-prop still works with provider/store until demotion.
5. npm run gate green.

Out of scope

• Full store / validation-* package demotion (Cleanup: drop validation-* packages, slim useFormTree, finalize ADRs #126).
• Parity matrix / async fixtures (Parity proof: full capability matrix across native + RHF + TanStack (own the matrix) #125).
• Native recipe move (Native-forms validation recipe behind the seam (verbatim) #122).

Relationships

• Parent: Wayfinder: demote validation to a non-goal (library renders errors, recipes produce them) #116
• Implements: Lock the field error-presentation seam #117 (plan → code)
• Blocked by: none — takeable now that RHF validation recipe behind the seam #123/TanStack Form validation recipe behind the seam #124 recipes are on main
• Related: Parity proof: full capability matrix across native + RHF + TanStack (own the matrix) #125 (parity), Native-forms validation recipe behind the seam (verbatim) #122 (native), Cleanup: drop validation-* packages, slim useFormTree, finalize ADRs #126 (demote store after parity)
• Evidence of friction: examples/basic-react/src/{fieldPresentation,rhfFieldControls,tanstackFieldControls}.recipe.tsx (merged via feat(examples): form-library recipes — RHF + TanStack over JSON Schema and Zod, layered and parity-proven #127)

[timkindberg]

Filed post-#127 merge so we can play the locked #117 library seam without blocking on native (#122) or full parity (#125).

[timkindberg]

Done

Landed the #117 inject seam and thinned the #127 recipe shells onto it.

• <Default of={field} errors={ValidationError[]} /> — present == show; omit-prop keeps store/ValidationProvider until Cleanup: drop validation-* packages, slim useFormTree, finalize ADRs #126
• Library field error lists: no role="alert" (a11y via aria-invalid / aria-describedby + fieldErrorId)
• useControlA11yProps() for hand-wired controls under the field root
• Recipes: deleted FieldShell / FieldErrors / a11yAttrs; RHF/TanStack keep only control wiring + error → ValidationError[] normalization
• Tests: injected-errors.test.tsx + a11y assertions updated
• npm run gate green

Unblocks #122 (native recipe) and feeds #126 (store demotion).