Summary

Adds optional validation field support for free_text and free_text_with_unit instruction types, enabling min/max bounds on user input. Validation logic is deferred to the backend — the CLI passes the field through and surfaces API errors directly.

Validation Schema

{
  "type": "number" | "string",
  "min": number | null,
  "max": number | null
}

• free_text: validation is a top-level field on the instruction
• free_text_with_unit: validation is per-unit_option (each unit can have different bounds)
• type is required; min/max are nullable (null = unbounded in that direction)

Usage Examples

Collection JSON with free_text string validation (character count bounds):

{
  "order": 1,
  "type": "free_text",
  "description": "How was your experience completing this task?",
  "validation": {
    "type": "string",
    "min": 10,
    "max": 500
  }
}

Collection JSON with free_text_with_unit per-unit number validation:

{
  "order": 3,
  "type": "free_text_with_unit",
  "description": "What is your current weight?",
  "unit_options": [
    {
      "label": "KG",
      "value": "kg",
      "validation": { "type": "number", "min": 20, "max": 300 }
    },
    {
      "label": "Pounds",
      "value": "lbs",
      "validation": { "type": "number", "min": 44, "max": 660 }
    }
  ],
  "default_unit": "kg",
  "unit_position": "suffix"
}

Implementation

• Added ValidationRule struct to model/collection.go and client/payloads.go
• Added Validation field to Instruction, UnitOption, PageInstruction, and CollectionPageItem structs
• Min/Max use *float64 without omitempty — backend requires explicit null (not field absence) for unbounded values
• No CLI-side validation — backend is the single source of truth for validation rules
• Updated example files with validation usage

Testing

Unit tests:

• Passthrough tests for number and string validation on free_text instructions
• Passthrough test for free_text_with_unit with per-unit-option validation
• Validation with only type specified (no min/max)
• Explicit null validation handled correctly

Manually verified against dev:

• free_text with string validation (min/max char count) — created successfully
• free_text_with_unit with per-unit number validation — created successfully
• Unbounded max (null) — created successfully
• Invalid validation type — backend error surfaced correctly
• min > max — backend error surfaced correctly
• DynamoDB records confirmed all validation fields persisted correctly