fix(python): PLR0915 counts statements, not lines

Verified with `ruff rule PLR0915`: it is `too-many-statements` (default 50),
not a line-length rule. Ruff has no line-based function-length rule at all.
python.md now says so and points both limits at a pytest case; coding-dev.md
gains the general distinction between a real length lint and a proxy.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

code-languages/python.md

@@ -132,9 +132,11 @@ When talking to a rate-limited API (a chat platform, a store, a tracker):
   installable package** with its own repo and version, consumed as a dependency.
 - Keep persistent state in the framework's own config/storage system so it survives restarts;
   do not invent a parallel JSON file beside it.
-- File and function size limits from the general rules apply — Ruff's `PLR0915` covers
-  function length; put the file limit in a pytest case (see
-  [`coding-dev.md` §4](skills-public/coding-dev.md)).
+- File and function size limits from the general rules apply. Ruff has **no line-based**
+  function-length rule — `PLR0915` (`too-many-statements`, default 50) and `C901`
+  (cyclomatic complexity) are the closest proxies and are worth enabling, but neither
+  measures lines. Put **both** the function-length and file-length limits in a pytest
+  case (see [`coding-dev.md` §4](skills-public/coding-dev.md)).
 
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