chore: remove dead cookiecutter regeneration infrastructure (#47)

## Summary

The repo was bootstrapped from `cookiecutter-pylibrary`. The
regeneration scaffolding has been sitting around since then — unused,
out of date, and in some cases pointing at infrastructure (AppVeyor)
that hasn't been part of CI for years. This PR knocks it all down in one
sweep so nothing dead-by-design remains in the tree.

10 files changed, **+13 / -314**.

## Removed

- `.cookiecutterrc` — cookiecutter regen metadata.
- `ci/bootstrap.py` — entry point for regenerating workflow files from
the templates.
- `ci/templates/` (whole directory):
  - `.appveyor.yml` template — AppVeyor isn't wired up.
- `.github/workflows/github-actions.yml` Jinja template — the live
workflow has evolved past it via #32, #35, #37.

## Coupled updates

- `tox.ini` — dropped the `[testenv:bootstrap]` env (calls deleted
`bootstrap.py`) and the `bootstrap` reference in the basepython
selector.
- `MANIFEST.in` — removed `include .cookiecutterrc`.
- `setup.cfg` — removed `ci/templates` from the flake8 `exclude` and
isort `skip` lists.
- `.pre-commit-config.yaml` — removed `ci/templates` from the top-level
`exclude` regex.
- `tests.local.sh` — replaced the per-version `if/elif` chain (which
still listed Python 3.7 and missed 3.12-3.14) with a single programmatic
`tox -e py$VERSION` lookup against `tox --listenvs-all`.
Self-maintaining when the matrix changes.
- `CHANGELOG.rst` — added a Housekeeping bullet for this PR under `0.3.0
(unreleased)`.

## Live and untouched

`ci/requirements.txt` is installed by every CI workflow (`pip install -r
ci/requirements.txt`). Not regen-related.

After this lands there should be **no dead infra** left in the tree.

Closes #46

1 files changed, 0 insertions, 65 deletions

diff --git a/ci/templates/.github/workflows/github-actions.yml b/ci/templates/.github/workflows/github-actions.yml
deleted file mode 100644
index eb42d88..0000000
--- a/ci/templates/.github/workflows/github-actions.yml
+++ /dev/null
@@ -1,65 +0,0 @@
-name: build
-on: [push, pull_request]
-jobs:
-  test:
-    name: {{ '${{ matrix.name }}' }}
-    runs-on: {{ '${{ matrix.os }}' }}
-    timeout-minutes: 30
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - name: 'check'
-            python: '3.9'
-            toxpython: 'python3.9'
-            tox_env: 'check'
-            os: 'ubuntu-latest'
-          - name: 'docs'
-            python: '3.9'
-            toxpython: 'python3.9'
-            tox_env: 'docs'
-            os: 'ubuntu-latest'
-{% for env in tox_environments %}
-{% set prefix = env.split('-')[0] -%}
-{% if prefix.startswith('pypy') %}
-{% set python %}pypy-{{ prefix[4] }}.{{ prefix[5] }}{% endset %}
-{% set cpython %}pp{{ prefix[4:5] }}{% endset %}
-{% set toxpython %}pypy{{ prefix[4] }}.{{ prefix[5] }}{% endset %}
-{% else %}
-{% set python %}{{ prefix[2] }}.{{ prefix[3:] }}{% endset %}
-{% set cpython %}cp{{ prefix[2:] }}{% endset %}
-{% set toxpython %}python{{ prefix[2] }}.{{ prefix[3:] }}{% endset %}
-{% endif %}
-{% for os, python_arch in [
-    ['ubuntu', 'x64'],
-    ['windows', 'x64'],
-    ['macos', ''],
-] %}
-          - name: '{{ env }} ({{ os }})'
-            python: '{{ python }}'
-            toxpython: '{{ toxpython }}'
-            {% if python_arch %}python_arch: '{{ python_arch }}'
-            {% endif %}tox_env: '{{ env }}{% if 'cover' in env %},codecov{% endif %}'
-            os: '{{ os }}-latest'
-{% endfor %}
-{% endfor %}
-    steps:
-    - uses: actions/checkout@v2
-      with:
-        fetch-depth: 0
-    - uses: actions/setup-python@v2
-      with:
-        python-version: {{ '${{ matrix.python }}' }}
-        architecture: {{ '${{ matrix.python_arch }}' }}
-    - name: install dependencies
-      run: |
-        python -mpip install --progress-bar=off -r ci/requirements.txt
-        virtualenv --version
-        pip --version
-        tox --version
-        pip list --format=freeze
-    - name: test
-      env:
-        TOXPYTHON: '{{ '${{ matrix.toxpython }}' }}'
-      run: >
-        tox -e {{ '${{ matrix.tox_env }}' }} -v