fix: camelize nested keys in read action typed map metadata

[mike1o1]

Summary

Fixes #62

When a read action has metadata containing typed maps (e.g., {:array, :map} with field constraints), the codegen correctly generates camelCase TypeScript types, but the runtime RPC response returns snake_case nested keys. Mutation metadata is unaffected because it follows a separate formatting path through format_field_names/2.

Root cause

do_add_read_metadata merges raw metadata values into the result record. The record then goes through OutputFormatter.format_map, which looks up each key via ResourceFields.get_public_field_type_info. Since metadata fields aren't resource attributes, the type comes back as nil, and ValueFormatter.format/5 short-circuits, returning nested map values with their original atom keys unchanged.

Fix

Apply format_field_names/2 to each metadata value in do_add_read_metadata before merging into the record. This recursively camelizes nested map keys while leaving the metadata keys as atoms for OutputFormatter to handle in Stage 4, consistent with how resource attribute keys are formatted.

Scalar metadata values (strings, integers, booleans) pass through format_field_names unchanged via the other -> other clause, so existing behavior is preserved.

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[Torkan]

Thanks for spotting this one! 😄

I'll merge it as-is, but also follow up with some minor changes to ensure that composite types without constraints, like :map for example, will get passed through as-is.