docs: complete Models agent-guide audit

[stefan-jansen]

Summary

• review the public guide against current model families, integrations, and hardware qualification
• record semantic maintenance triggers and the public/private boundary
• replace the obsolete private sidecar orientation and reconcile all four local issue drafts

Verification

• uv run ruff check src/ tests/ examples/ scripts/
• uv run ruff format --check src/ tests/ examples/ scripts/
• uv run ty check
• uv run pytest tests/ -q --cov-report=json:coverage.json (422 passed)
• uv run python scripts/ci/check_coverage.py coverage.json
• uv run mkdocs build --strict
• uv build
• actionlint
• pre-commit run --all-files
• ecosystem audit-workspaces check for Models

Closes #50
Tracked by ml4t/ecosystem#38.

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