Refactor fields() to return raw schema data, move form logic to @b9g/forms

[brainkim]

Problem

fields() currently returns FieldMeta which mixes three concerns:

1. Database metadata (primaryKey, autoIncrement, inserted, etc.) - from .db.*() methods
2. Form interpretation (type: "email" | "textarea", required, etc.) - computed/inferred
3. Zod constraints (min, max, minLength, maxLength, options) - extracted from schema internals

This creates problems:

• Form logic doesn't belong in a database library
• HTML input types (FieldType) are opinionated and leak into core
• Consumers can't easily access raw db metadata without the "cooking"
• The flattened structure loses information

Solution

1. Simplify fields() to return raw data

interface FieldInfo {
  name: string;
  schema: ZodType;        // raw Zod schema
  db: FieldDBMeta;        // raw db metadata from .db.*()
}

interface Relation {
  table: Table;
  fields(): TableFields;  // navigate to related table
}

type TableFields = Record<string, FieldInfo | Relation>;

2. Remove from Zen

• FieldType (HTML input types)
• FieldMeta (the cooked/flattened type)
• extractFieldMeta() (the cooking function)
• Computed properties: type, required, min, max, minLength, maxLength, options

3. Create @b9g/forms (separate package)

Headless schema introspection for form generation:

• Zod type inference → field types
• Constraint extraction → validation hints
• Db-awareness → skip auto-generated fields, handle relations
• Works with any form library (TanStack Form, RHF, etc.)

Breaking Changes

• fields() return type changes from FieldMeta to FieldInfo
• FieldType and FieldMeta exports removed
• Consumers needing form metadata should use @b9g/forms (or access schema.meta() directly)

Migration

// Before
const fields = Users.fields();
fields.email.type;        // "email"
fields.email.required;    // true

// After  
const fields = Users.fields();
fields.email.schema;              // ZodString (use Zod APIs)
fields.email.db.autoIncrement;    // boolean
fields.email.schema.isOptional(); // use Zod directly

// Or use @b9g/forms for form-specific metadata
import { formFields } from "@b9g/forms";
const form = formFields(Users);
form.email.type;          // "email"
form.email.required;      // true

Related

• Addresses the underlying issue from FieldMeta should expose hasDefault/autoIncrement for primary keys #13 (raw db metadata access)
• Related to Validation runs on read despite documentation stating otherwise #14: removing validation from fields() introspection aligns with the principle that validation should happen on writes, not reads/introspection

[brainkim]

It’s not clear what project is going to own @b9g/forms, so that’s up in the air right now.