chore(linguist): exclude Python from language detection

Estate-wide policy: Python is banned outside SaltStack contexts. Pending eradication (issue tracked separately); this PR is the immediate cosmetic fix to stop the language showing up in GitHub's primary-language detection.

Part of estate-wide metadata cleanup 2026-05-26.

Author: hyperpolymath

.gitattributes

@@ -52,3 +52,5 @@ Containerfile  text eol=lf
 # Lock files
 Cargo.lock  text eol=lf -diff
 flake.lock  text eol=lf -diff
+# Pending estate-wide policy: hide Python from primary-language detection.
+**/*.py linguist-detectable=false