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
+- File and function size limits from the general rules apply. Ruff has **no line-based**
-  function length; put the file limit in a pytest case (see
+  function-length rule — `PLR0915` (`too-many-statements`, default 50) and `C901`
-  [`coding-dev.md` §4](skills-public/coding-dev.md)).
+  (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)).
 
 ---
 

coding-dev.md

@@ -147,8 +147,10 @@ depends on those.
 A limit nobody checks is a suggestion. Pick the **highest** applicable option:
 
 1. **A linter rule**, where one exists — the function limit is usually covered natively
-   (Clippy's `too_many_lines`, ESLint's `max-lines-per-function`, `golangci-lint`'s `funlen`,
+   (Clippy's `too_many_lines`, ESLint's `max-lines-per-function`, `golangci-lint`'s `funlen`).
-   Ruff's `PLR0915`). A function that trips it wants extracting, not a suppression.
+   A function that trips it wants extracting, not a suppression. Note that some linters only
+   offer *proxies* for length — Ruff's `PLR0915` counts statements, not lines — in which case
+   enable the proxy and put the real limit in a test.
 2. **A test**, for anything the linter does not cover — file length almost always falls here.
    A test is the best home for it: it runs with the suite everyone already runs, it needs no
    extra tooling, it fails with a message naming the offending files, and it travels with the