fix: accept JSON schemas in structured output parser

[Iams4kura]

Summary

• Fixes: Passing a supported JSON Schema dictionary into structured-output generation raises TypeError before any model request instead of parsing the returned dictionary.
• Root cause: get_structured_output_parser documents and types dictionaries as valid schemas but calls the class-only issubclass builtin before dispatching dictionary schemas to _dict_output_parser.

Regression evidence

• Before: PYTHONDONTWRITEBYTECODE=1 uv run --frozen pytest -o addopts='' -p no:cacheprovider tests/utils/output_parser_test.py::test_structured_output_parser_accepts_json_schema -q exited 1

• After: PYTHONDONTWRITEBYTECODE=1 uv run --frozen pytest -o addopts='' -p no:cacheprovider tests/utils/output_parser_test.py::test_structured_output_parser_accepts_json_schema -q exited 0

Verification

• PYTHONDONTWRITEBYTECODE=1 .venv/bin/pytest -o addopts='' -p no:cacheprovider tests/utils/output_parser_test.py -q
• PYTHONDONTWRITEBYTECODE=1 .venv/bin/pytest -o addopts='' -p no:cacheprovider tests/test_json_scraper_graph.py -q
• .venv/bin/ruff check scrapegraphai/utils/output_parser.py tests/utils/output_parser_test.py
• .venv/bin/black --check scrapegraphai/utils/output_parser.py tests/utils/output_parser_test.py
• .venv/bin/isort --check-only scrapegraphai/utils/output_parser.py tests/utils/output_parser_test.py
• uv build --no-sources
• offline ChatOpenAI.with_structured_output JSON Schema contract check

Scope

• 2 files changed, +18 / -1 lines

Local full-suite note

I also attempted the repository CI selection, uv run pytest tests/ -m "unit or not integration". It reached 95% with unrelated live-provider, browser, network, and existing assertion failures, then was interrupted when an external proxy request stalled. The deterministic affected suites listed above pass.