deps: remove langchain dependency (#1869)

Remove langchain and associated dependencies to simplify the codebase
and reduce exposure to third-party dependency issues.

Removed dependencies:
- langchain~=0.3.10
- langchain-core~=0.3.81
- langchain-ollama~=0.3.5
- langchain-text-splitters~=0.3.11

Removed files:
- ansible_ai_connect/ai/api/model_pipelines/langchain/ (entire directory)
  - configuration.py
  - pipelines.py
  - tests/test_pipeline.py

Refactored ollama module to be fully self-contained:

Configuration (ollama/configuration.py):
- Created OllamaConfiguration extending BaseConfig directly
- Created OllamaBasePipelineConfiguration
- Removed dependency on langchain configuration classes

Pipelines (ollama/pipelines.py):
- Created custom OllamaClient for direct Ollama API communication
- Moved all utility functions from langchain module:
  * message_to_string()
  * create_role_outline()
  * unwrap_role_answer()
  * unwrap_message_with_yaml_answer()
  * unwrap_playbook_answer()
  * unwrap_task_answer()
- Implemented all pipeline classes without langchain:
  * OllamaMetaData
  * OllamaCompletionsPipeline
  * OllamaPlaybookGenerationPipeline
  * OllamaRoleGenerationPipeline
  * OllamaRoleExplanationPipeline (returns "nop" health check - not implemented)
  * OllamaPlaybookExplanationPipeline

Tests (ollama/tests/test_pipelines.py):
- Migrated relevant tests from deleted langchain/tests/test_pipeline.py
- Added comprehensive test coverage for:
  * Unwrap functions (task, playbook, role, message parsing)
  * Completions pipeline with mocked requests.post
  * Playbook generation pipeline (with and without outline, custom prompt)
  * Role generation pipeline (with and without outline)
  * Playbook explanation pipeline (with custom prompt)
- All tests updated to mock requests.post instead of langchain's FakeListLLM
- Prevents AttributeError from patching non-existent symbols

Updated configuration:
- pyproject.toml: Removed langchain dependencies and pyright path
- requirements.txt: Regenerated without langchain (15 fewer packages)
- uv.lock: Regenerated without langchain dependencies
- .github/workflows/pyright.yml: Removed langchain from CI dependencies

All functionality preserved. Type checking passes with pyright.

Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: goneri

.github/workflows/pyright.yml

@@ -21,5 +21,5 @@ jobs:
         python-version: '3.12'
     - name: install
       run: |
-        pip install pyright django boto3 requests prometheus_client backoff django_prometheus langchain langchain-ollama django-health-check aiohttp ansible-lint ansible_anonymizer
+        pip install pyright django boto3 requests prometheus_client backoff django_prometheus django-health-check aiohttp ansible-lint ansible_anonymizer
         pyright

ansible_ai_connect/ai/api/model_pipelines/__init__.py

@@ -2,7 +2,6 @@
 import ansible_ai_connect.ai.api.model_pipelines.dummy.pipelines  # noqa
 import ansible_ai_connect.ai.api.model_pipelines.http.configuration  # noqa
 import ansible_ai_connect.ai.api.model_pipelines.http.pipelines  # noqa
-import ansible_ai_connect.ai.api.model_pipelines.langchain.pipelines  # noqa
 import ansible_ai_connect.ai.api.model_pipelines.llamacpp.configuration  # noqa
 import ansible_ai_connect.ai.api.model_pipelines.llamacpp.pipelines  # noqa
 import ansible_ai_connect.ai.api.model_pipelines.llamastack.configuration  # noqa