fix(coding-dev): prefer a test over the build script for size limits

A shell check only runs where that script runs. A test travels with the repo,
needs no extra tooling, and fails with a message naming the offending files.
Enforcement is now a preference order: native linter rule > test > build
script as fallback, with a worked example and a note on why a per-compile
build hook usually is not worth the incremental-build cost.

Propagated per language: rust (clippy has no file-length lint -> workspace
root test), js-typescript (ESLint max-lines covers both natively, no test
needed), go/python/csharp (linter for functions, test for files), bash (don't
reimplement in the gate what a test can assert).

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

code-languages/python.md

@@ -132,7 +132,9 @@ 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.
+- 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)).
 
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