chore: remove vestigial setup.cfg, add [tool.wads.ci], migrate CI to the stub

[thorwhalen]

Summary

Found via a Priority E doctor-sweep pass (AI enablement / README-vs-code / wads-setup audit):

• Removed setup.cfg. It was pure legacy cruft -- pyproject.toml has been the real SSOT for a while (hatchling backend, full [project] metadata matching), nothing in the repo referenced setup.cfg except a stale CI comment ("MIGRATION NOTE: Old CI references setup.cfg - ensure project is migrated to pyproject.toml first"), and its only activity was the CI bot's version-bump push-back keeping its version = in sync with a value nothing actually read.
• Added [tool.wads.ci]. It was entirely absent even though ci.yml already reads it (silently falling back to the read-ci-config action's defaults) -- added project_name = "config2py" and testing.python_versions = ["3.10", "3.12"] explicitly.
• Migrated CI to the reusable-workflow stub. Was on "Modern uv (inline)", CI green -> sanctioned moment per the wads-migrate skill.

Everything else checked clean: no .claude/ (fact, not staleness); README's "For AI agents" section (added by #20 last week) is accurate; config_getter, is_repl, and the codec/extras story all match the current source.

Config-only change; self-reviewed only.

Test plan

• wads ci-local green (ruff format+lint, pytest 3.10+3.12, 132 tests + 4 skipped, build)
• Hosted CI green (this repo may hit the same first-migration action_required anomaly diagnosed on ci: migrate to the reusable uv-ci stub py2mcp#15, ci: migrate to the reusable uv-ci stub thorwhalen/artful#11, ci: migrate to the reusable uv-ci stub thorwhalen/skill#10 in this session -- if so, see those PRs)

🤖 Generated with Claude Code

https://claude.ai/code/session_011HSBVhDjRU4apSLcRkavv9

[thorwhalen]

Same action_required/zero-jobs anomaly as i2mint/py2mcp#15, thorwhalen/artful#11, thorwhalen/skill#10 (4th confirmation this session) -- hits every repo's FIRST-ever call to i2mint/wads/.github/workflows/uv-ci.yml@master, never a repo already on it. wads ci-local is fully green locally. Leaving this PR open; filed a manual-task issue.

Self-reviewed only (config-only change, no application code behaviour altered).

[thorwhalen]

Verified from the API at the end of the 2026-09-22 crowsnest run: this run sits at action_required with zero jobs, POST /actions/runs/{id}/approve refuses it ("not from a fork pull request"), and rerun refuses it too. It needs the one-time approval button in this repo's Actions tab — the first call to the shared reusable workflow. wads ci-local is green on this branch; nothing else blocks the merge.