feat: DIA-1322: Use field_schema in skills as primary output format

[niklub]

If Skill is provided with field_schema JSON, other output formatters like output_template, labels are ignored.

Additional changes in this PR:

• rewrite some tests to ensure they pass existing stubs (verifying nothing has changed)
• any Runtime execution now requires response_model (breaking change for those who use runtimes directly)

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Commit https://github.com/HumanSignal/infra/commit/263266f880bde017e2484e33b69cf9fafb78b7ae is created.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 79.48718% with 24 lines in your changes missing coverage. Please review.

Project coverage is 60.30%. Comparing base (2c8214d) to head (3a105ac). Report is 2 commits behind head on master.

Files	Patch %	Lines
adala/skills/collection/entity_extraction.py	63.63%	16 Missing :warning:
adala/skills/collection/classification.py	87.50%	4 Missing :warning:
adala/runtimes/_litellm.py	33.33%	2 Missing :warning:
adala/skills/_base.py	93.75%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #185 +/- ## ========================================== + Coverage 59.47% 60.30% +0.83% ========================================== Files 43 44 +1 Lines 1905 2081 +176 ========================================== + Hits 1133 1255 +122 - Misses 772 826 +54 ```

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Commit https://github.com/HumanSignal/infra/commit/c18ad022d4ce12c18ad4c78710a124168e8f510c is created.

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Commit https://github.com/HumanSignal/infra/commit/2f057d1e5583d438d4b09849c7047ea8f58be34b is created.

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Commit https://github.com/HumanSignal/infra/commit/be40eb98a9322e7701f633fa500a69a6ea991eb5 is created.

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Commit https://github.com/HumanSignal/infra/commit/94721699b54ec6ec698e6280c2e75d618ccf724d is created.