fix(ci): add ruff to the python dev dependency-group (codegen format pass)

The last Python conformance failure (uncovered once the pydantic fix let the step
reach it): tests/codegen/test_cli_registry runs codegen, whose format pass
(src/metaobjects/codegen/format.py) shells out to `ruff` — but `ruff`, like pydantic,
lived only in [project.optional-dependencies], not the [dependency-groups] that
`uv run` installs. So CI failed with "No module named ruff". Add ruff to the group
and relock.

Verified via the full CI `uv run` sequence: conformance 267, validation 9,
cli-registry 5 — all green. This was the 7th and final pre-existing red layer on
main; with it, every required check passes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: dmealing

server/python/pyproject.toml

@@ -98,4 +98,8 @@ dev = [
     # imports pydantic to exercise the generated Pydantic models, so it must be here
     # or the CI `uv run pytest` collection fails with ModuleNotFoundError.
     "pydantic>=2",
+    # ruff is the Python codegen format pass (src/metaobjects/codegen/format.py); the
+    # cli-registry corpus runs codegen, so without ruff in the group `uv run pytest`
+    # fails at format time with "No module named ruff".
+    "ruff>=0.6",
 ]