[lucaosti]

What

Tool configuration in the root pyproject.toml:

• ruff: py311, line length 100, rule sets E,F,W,I,B,UP,SIM,RUF,D with Google docstrings. D is ignored under tests/.
• mypy: strict = true on packages/.
• pytest: coverage for agentic_rag and agentic_rag_code, --cov-fail-under=80.
• import-linter, three contracts:
  1. agentic_rag.types and agentic_rag.ports never import agentic_rag.adapters.
  2. agentic_rag never imports agentic_rag_code.
  3. Engine layers, from top to bottom: adapters, then ingest : retrieval : generation : agent : eval, then evidence, then ports, then types.

It also adds skeleton engine subpackages, each with a one-line docstring, so that the contracts resolve.

Why

M0-2 of the backlog, following spec section 9 and ADR-0001.

One deviation from the backlog text: the middle layer uses non-independent siblings (:) instead of independent ones (|). The agent runtime (E4) and the eval runner (M2-3) must be able to import retrieval.

Closes #3

How verified

uv run ruff check . && uv run ruff format --check .
uv run mypy
uv run lint-imports
uv run pytest -q

Results:

Check	Result
ruff	all checks passed
mypy	no issues in 13 files
import-linter	3 contracts kept
pytest	2 passed, coverage 100%

Negative check: I added import agentic_rag.adapters to types/__init__.py locally. The result was Contracts: 1 kept, 2 broken. The change was then reverted.

Reviewer notes

This PR is stacked on #45. Its base becomes main automatically once #45 is merged.

[lucaosti]

Merged without an approving review by maintainer decision, to unblock contributors: this is the foundation chain everything else depends on. Verified locally on the combined chain (#1, #45, #46, #47, #49, #50 merged together, no conflicts): uv sync --locked, ruff check and format, mypy, import-linter (3 contracts kept), pytest with 100% coverage.