Drop the unused flake8rc, and the three places that claimed it was used

flake8rc was a committed snapshot of the global flake8 config. Nothing read it:
CI lints with ruff, and Emacs flycheck reads ~/.config/flake8 by absolute path
(flycheck-flake8rc in init.el), not the project copy. It had also drifted from the
global — missing F824, differing around W504 — so as documentation it was actively
misleading.

Three stale references went with it:

- CLAUDE.md claimed it was "used by Emacs flycheck". It isn't.
- coverage.yml did `pip install flake8` and then never ran flake8. Dead step.
- ci.yml's header comment said the workflow was customized to "use the local
  flake8rc", which it isn't, and to test with `unpythonic.setup.fixtures`, which
  does not exist — the module is `unpythonic.test.fixtures`.

The global config (~/.spacemacs.d/flake8, public repo, symlinked to ~/.config/flake8)
remains the single source of truth for the legacy flake8 setup; ruff is the enforced
linter.

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

Author: Technologicat

.github/workflows/ci.yml

@@ -1,7 +1,7 @@
 # This workflow will install Python dependencies, run tests and lint with a variety of Python versions
 # For more information see: https://help.github.com/actions/language-and-framework-guides/using-python-with-github-actions
 #
-# This version is customized to install with pdm, use the local flake8rc, and test with unpythonic.setup.fixtures.
+# This version is customized to install with pdm, lint with ruff, and test with unpythonic.test.fixtures.
 
 name: Python package
 

.github/workflows/coverage.yml

@@ -30,7 +30,6 @@ jobs:
     - name: Install tools in CI virtualenv
       run: |
         python -m pip install --upgrade pip
-        pip install flake8
         pip install pdm
     - name: Create in-project virtualenv and install dependencies
       run: |

CLAUDE.md

@@ -109,8 +109,6 @@ Part of unpythonic's **public API** (`unpythonic.test.fixtures`, `unpythonic.tes
 ruff check <changed .py files>   # primary linter (config in pyproject.toml)
 ```
 
-Legacy `flake8rc` also present (used by Emacs flycheck, not by CI or CC).
-
 ## Code structure and conventions
 
 - **Regular code** in `unpythonic/`, **macros** in `unpythonic/syntax/`, **REPL networking** in `unpythonic/net/`, **dialects** in `unpythonic/dialects/`.