chore: add ANN type annotations to faiss, fastembed, firecrawl, github, google_ai

[julian-risch]

Related Issues

Proposed Changes

Enable ruff's ANN ruleset (flake8-annotations) for five integrations and fix all resulting violations. Changes are consistent across all integrations:

• faiss: Enable ANN in ruff config; add -> None to __init__ in FAISSDocumentStore and FAISSEmbeddingRetriever; add -> None to _create_new_index
• fastembed: Enable ANN in ruff config; add -> None to __init__ in _FastembedEmbeddingBackend, _FastembedSparseEmbeddingBackend, and FastembedRanker; add -> None to warm_up in FastembedRanker
• firecrawl: Enable ANN in ruff config only (all annotations were already present)
• github: Enable ANN in ruff config; add -> None to __init__ in all 6 connector classes and 6 tool classes
• google_ai: Enable ANN in ruff config; add -> None to __init__ in both generators; add -> "GoogleAIGeminiGenerator" to __new__ with proper *_: Any and **kwargs: Any annotations; add -> dict[str, list[str]] / -> dict[str, list[ChatMessage]] to run and run_async methods

For all integrations:

• Added "ANN" to ruff select
• Added "ANN401" to ruff ignore (allow Any at SDK/dynamic boundaries)
• Added "ANN" to tests/**/* per-file-ignores (tests don't need type annotations)

How did you test it

• Ran hatch run fmt-check for all 5 integrations — all pass
• Ran hatch run test:types for all 5 integrations — all pass (google_ai pre-existing errors are unchanged)
• Verified ruff check --select ANN --ignore ANN401 reports zero violations across all 5 integrations

Notes for reviewer

google_ai has pre-existing mypy errors unrelated to this PR. It's archived anyway.

Checklist

• I have read the contributing guidelines
• I have updated the related documentation if needed
• I have added tests for the changes I made (N/A - annotation-only changes)
• I have run hatch run test:types and all checks pass
• I have run hatch run fmt-check and all checks pass

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