fix: recursive array/object JSON Schema in tool params across all runtimes

[sethjuarez]

Problem

Tool parameter schemas with nested arrays and objects produced flat JSON Schema like {"type": "array"} without items, and {"type": "object"} without nested properties. This caused LLMs to invent their own field names inside array items, leading to undefined values in the caller's code.

Example — this .prompty tool definition:

parameters:
  - name: encounters
    kind: array
    items:
      kind: object
      properties:
        - name: title
          kind: string
        - name: difficulty
          kind: integer

Before (sent to LLM):

{ "encounters": { "type": "array" } }

After (sent to LLM):

{
  "encounters": {
    "type": "array",
    "items": {
      "type": "object",
      "properties": {
        "title": { "type": "string" },
        "difficulty": { "type": "integer" }
      },
      "required": ["title", "difficulty"],
      "additionalProperties": false
    }
  }
}

Root Cause

The schema emitter types (ArrayProperty.items, ObjectProperty.properties) were already correct — ArrayProperty has items: Property and ObjectProperty has properties: list[Property]. The bug was in the hand-written wire-format conversion functions that mapped these to flat JSON Schema without recursing.

Fix

Replace flat schema conversion with recursive property→JSON Schema logic in all runtimes:

Runtime	File	What Changed
Python OpenAI/Azure/Foundry	providers/openai/executor.py	_schema_to_wire delegates to _property_to_json_schema
Python Anthropic	providers/anthropic/executor.py	Same pattern
TypeScript OpenAI	packages/openai/src/wire.ts	schemaToWire delegates to propertyToJsonSchema
TypeScript Anthropic	packages/anthropic/src/wire.ts	Same pattern
C#	Prompty.Core/SchemaHelpers.cs	New recursive PropertyToJsonSchema() method
Rust OpenAI	prompty-openai/src/wire.rs	New property_to_json_schema() for tools + outputs
Rust Anthropic	prompty-anthropic/src/wire.rs	Same for tools

Note: Structured output was already correct in Python and TypeScript (they had a separate recursive path). C# and Rust structured output was also flat and is now fixed.

Tests

• Python: 43 OpenAI executor tests + 36 Anthropic tests pass (3 + 2 new nested schema tests)
• C#: 21 schema helper tests pass (3 new: ArrayOfObjects, NestedObject, DeeplyNested)
• TypeScript: 3 new tests added (same pre-existing @prompty/core resolution issue blocks test runner)
• Rust: Compiles clean (cargo check) for both prompty-openai and prompty-anthropic