Fix: OpenAI o-series and gpt-3.5 model IDs route to no provider

[Karthick-dev-cart]

Description

Fixes #492

Bug fix

OPENAI_PATTERNS in langextract/providers/patterns.py only matched gpt-4/gpt4./gpt-5/gpt5. prefixes. Any OpenAI o-series reasoning model id (o1, o3, o3-mini, o4-mini, ...) or a legacy gpt-3.5-turbo-style id matched no provider pattern at all, so factory.create_model() raised InferenceConfigError: no provider found instead of routing to the OpenAI provider. Adds the two missing patterns (^gpt-3\.5, ^o[1-9]).

How Has This Been Tested?

Added tests/patterns_test.py with two tests:

• test_reasoning_and_legacy_openai_models_resolve_to_openai_provider -- verifies o-series (o1, o1-mini, o3, o3-mini, o4-mini) and gpt-3.5-turbo all resolve to the OpenAI provider via the router, as subtests.
• test_ollama_gpt_oss_pattern_is_unaffected -- guards against the new o[1-9] pattern accidentally shadowing Ollama's existing gpt-oss model support.

$ python -m pytest tests/
61 passed, 3 skipped (pre-existing, unrelated -- missing API keys / no local Ollama)

Checklist:

• I have read and acknowledged Google's Open Source Code of conduct.
• I have read the Contributing page, and I either signed the Google Individual CLA or am covered by my company's Corporate CLA.
• I have discussed my proposed solution with code owners in the linked issue(s) and we have agreed upon the general approach.
• I have made any needed documentation changes, or noted in the linked issue(s) that documentation elsewhere needs updating.
• I have added tests, or I have ensured existing tests cover the changes
• I have followed Google's Python Style Guide and ran pylint over the affected code.

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[Karthick-dev-cart]

@googlebot I signed it!

[github-actions]

⚠️ Branch Update Required

Your branch is 1 commits behind main. Please update your branch to ensure CI checks run with the latest code:

git fetch origin main
git merge origin/main
git push

Note: Enable "Allow edits by maintainers" to allow automatic updates.