Add spec_file support to PydanticAIHook.create_agent

[gopidesupavan]

Add spec_file parameter to PydanticAIHook.create_agent to load
agent settings from a pydantic-ai AgentSpec YAML or JSON file instead
of hard-coding them in Python.

https://pydantic.dev/docs/ai/core-concepts/agent-spec/#loading-specs

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[Copilot]

Pull request overview

Adds a spec_file parameter to PydanticAIHook.create_agent, allowing agent configuration (model, instructions, model_settings, retries, etc.) to be loaded from a pydantic-ai YAML/JSON AgentSpec file via Agent.from_file(...) instead of being hard-coded in Python. Also bumps the pydantic-ai-slim minimum to >=1.72.0 (which introduced from_file) and adds docs plus an example DAG + example YAML spec.

Changes:

• Add spec_file parameter and new overloads to PydanticAIHook.create_agent; raise ValueError when neither instructions nor spec_file is given.
• Add docs section, example DAG, and example YAML spec for the new spec-file workflow.
• Bump pydantic-ai-slim minimum to >=1.72.0 in pyproject.toml, README, docs index, and uv.lock.

Reviewed changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
providers/common/ai/src/airflow/providers/common/ai/hooks/pydantic_ai.py	New spec_file branch in create_agent delegating to Agent.from_file with overloads.
providers/common/ai/tests/unit/common/ai/hooks/test_pydantic_ai.py	Adds tests for spec_file routing, Path support, instruction override, output_type, kwargs forwarding, and validation error.
providers/common/ai/src/airflow/providers/common/ai/example_dags/example_pydantic_ai_hook.py	New example DAG demonstrating spec_file use and instruction override.
providers/common/ai/src/airflow/providers/common/ai/example_dags/example_agent_spec.yaml	New example AgentSpec YAML file used by the example DAG.
providers/common/ai/docs/hooks/pydantic_ai.rst	New "Loading Agent Config from a Spec File" docs section with YAML sample and example include.
providers/common/ai/pyproject.toml	Bump pydantic-ai-slim minimum to >=1.72.0.
providers/common/ai/README.rst	Reflect bumped pydantic-ai-slim version.
providers/common/ai/docs/index.rst	Reflect bumped pydantic-ai-slim version.
uv.lock	Lockfile update for the bumped pydantic-ai-slim minimum.