v0.6.2 — JsonDeserializer tool-use envelope unwrap

Patch release for one fix landing in #22.

Fixed

• Normandy.LLM.JsonDeserializer now recovers from tool-use-style response envelopes (#22) — some vision/instruction-following LLMs (Nemotron-Nano-12B-VL on DigitalOcean Inference, some Llama variants) wrap their JSON in {"name": "...", "arguments": {...}} even when given response_format: {"type": "json_object"} and a system prompt asking for the bare object shape. parse_and_validate/3 previously cast such payloads to an all-defaults struct and returned :ok, so downstream consumers silently dropped every populated field. parse_and_populate/3 now retries the cast once against parsed["arguments"] when the outer attempt either succeeded with all-defaults OR returned a validation error, and the "arguments" value is itself a map. If the retry yields any populated field it wins; if it still yields all-defaults the original result is preserved so bare-shape responses see no behaviour change. One level only — {"arguments": {"arguments": {...}}} is not unwrapped. Inner cast errors are propagated when the inner map carries at least one permitted key (atom or string form), so e.g. {"arguments":{"count":"not_a_number"}} against count: :integer surfaces the validation error instead of returning an empty struct; inner errors are still suppressed when no permitted keys are present, so unrelated envelopes don't manufacture new failures. The {:ok, struct} / {:error, reason} contract is unchanged for every pre-existing shape.
• get_required_fields/1 in JsonDeserializer now reads required fields from the correct source (#22) — the helper was filtering __specification__/0 entries as if each were a metadata map, but Normandy.Schema stores {name, type} tuples there, so the filter never matched and validate_required/2 was being called with an empty list for every schema. It now reads __schema__(:required) (the source of truth) and falls back to the old scan for schemas that don't expose that callback. Required-field validation now actually fires for schemas declaring field :foo, _, required: true.

Full Changelog: v0.6.1...v0.6.2