fix: apply default tags via TextUnmarshaler

[vulragrag-star]

Summary

Types that implement encoding.TextUnmarshaler are modeled as strings in the schema, but convertType still used reflect.Convert for default tags. That panicked for wrappers such as a duration type with default:"10s" (schema type string, Go type not a string).

Changes

• Unmarshal string defaults through TextUnmarshaler in convertType for runtime defaults
• Keep the schema default in wire string form for OpenAPI (jsonTag)
• Add tests covering convertType, findDefaults, and SchemaFromField for TextUnmarshaler defaults

Fixes #680

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.20%. Comparing base (ef50837) to head (88bb960).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1126      +/-   ##
==========================================
+ Coverage   93.19%   93.20%   +0.01%     
==========================================
  Files          24       24              
  Lines        5008     5021      +13     
==========================================
+ Hits         4667     4680      +13     
  Misses        273      273              
  Partials       68       68              

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[vulragrag-star]

Added tests for pointer convertType path and invalid TextUnmarshaler defaults.
Tip: e4978cc1f6782f69ffe3c0dcd59cb8b5eea8b538.

[robtme]

Hey @vulragrag-star! I haven't properly reviewed this yet, but please move the tests into an existing test file rather than creating a new one. Thank you!

[vulragrag-star]

Moved the TextUnmarshaler default tests into huma_internal_test.go (existing package huma file).
Tip: 88bb96081eab7a7eace79e228f842deb144bd3a6.