🦞 igor-claw: fix Create Form recipe's identifier guidance for choice/date fields - #824

Problem

The Create Form recipe's own recommended pattern for choice/date fields causes the exact bug it warns about. It instructs setting identifier: "TEXT_INPUT" for RADIO_GROUP/DROPDOWN fields (Field Types Reference table + "Choice fields" example), and doesn't cover DATE_INPUT/DATE_PICKER at all.

Live-verified on wix.form_app.form via Create Form: the Form Schemas API (form-schema-service) derives a field's rendered componentType on every subsequent read from its identifier string, matched against an internal fixed allow-list — completely independent of the componentType actually set in the request. Following the recipe's own guidance (identifier: "TEXT_INPUT" + componentType: "RADIO_GROUP") makes the field's own create response immediately show componentType: "TEXT_INPUT", discarding radioGroupOptions — no error, HTTP 200. Setting identifier to match the componentType instead ("RADIO_GROUP", "DROPDOWN", "DATE_INPUT") reproducibly fixes it.

This is the root cause of an MCP feedback report where an agent built a lead-capture form with a dropdown "Preferred Campus" field and a "Date of Birth" field; both silently reverted to TEXT_INPUT after creation, and the DOB field's validation.format became immutably stuck at DATE even though its rendered type was lost.

Solution

• Corrected the "Field Types Reference" table and "Choice fields" example to use identifier matching componentType (RADIO_GROUP/DROPDOWN) instead of "TEXT_INPUT".
• Added a new "Date fields (DATE_INPUT / DATE_PICKER)" section (previously undocumented), with the same identifier-must-match-componentType rule.
• Updated the "CRITICAL" bullet and troubleshooting table to describe the actual failure mode: a mismatched identifier doesn't just risk a fallback, it unconditionally coerces the field to TEXT_INPUT (or drops it if identifier is fully custom).

Considerations - important facts the reviewer should know

• The underlying service behavior (silently overriding componentType based on an undocumented identifier allow-list instead of erroring) is a real API bug being raised separately with the Forms team — this PR only fixes the recipe so agents following it stop reproducing that bug.
• Filed automatically by an AI agent acting on behalf of Ayal (ayalg@wix.com), researching Wix MCP user feedback. Slack thread: https://wix.slack.com/archives/C08P5DKLJR5/p1785825864996019
• Did not touch the file's existing wrong appDefId (14ce1214-...) — that's already tracked by open PR 🦞 igor-claw: fix wrong Wix Forms appDefId in Create Form recipe #658.