fix: accept conftest.py as alternative to context.py, document test separation

[TheRealAgentK]

Summary

Two changes: a validation fix and documentation updates, both supporting the automated testing work in autohive-integrations PR #250.

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1. Fix: Accept conftest.py as alternative to context.py

Problem: validate_integration.py requires tests/context.py as a hard dependency. Integrations that have migrated to pytest use tests/conftest.py instead (for pytest fixture setup), and the validator fails with:

❌ Missing tests/context.py (Test context/import setup)

Fix: The validator now accepts either tests/context.py (legacy) or tests/conftest.py (pytest). At least one must be present.

Files changed:

• scripts/validate_integration.py — validation logic
• scripts/docs/validate_integration.md — updated checks table
• INTEGRATION_CHECKLIST.md — added conftest.py to lint suppression table

Context: 84 of 86 integrations still use context.py. Three integrations (hackernews, bitly, perplexity) have migrated to conftest.py as part of the pytest testing prototype. This change is backwards-compatible — existing integrations are unaffected.

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2. Docs: Unit/integration test separation

Documents the two-tier testing approach established in the integrations repo:

	Unit tests	Integration tests
File naming	test_*_unit.py	test_*_integration.py
Marker	@pytest.mark.unit	@pytest.mark.integration
Runs in CI	Yes (via run_tests.py)	Never
Auto-discovered	Yes	No — explicit file path required
Credentials	No (mocked)	Yes (from .env)

Files changed:

• LOCAL_DEVELOPMENT.md — added "Running Tests" section, added run_tests.py to CI table (was missing), updated required files list
• README.md — added note that run_tests.py is unit-only, updated required files list
• scripts/docs/run_tests.md — added "Unit Tests Only" section clarifying scope