Document provider foundation completion

[Th0rgal]

Closes #47.

Summary

• record the provider platform foundation tracker as complete
• mark WF-PROV-001 through WF-PROV-005 acceptance criteria complete
• add docs coverage tying the completion record to promotion gates, runtime manifests, conformance helpers, live-smoke evidence, and runtime profiles

Validation

• uv run ruff check src tests examples scripts
• uv run ruff format --check src tests examples scripts
• uv run python scripts/generate_provider_docs.py --check
• uv run mkdocs build --strict
• uv run pytest tests/test_docs_site.py -q
• uv run pytest -m "not live"
• bash scripts/test_package.sh