ci: exclude historical audit artifacts from prettier

The lint job started failing because prettier now reformats
docs/audit/01-coverage-baseline.md, a UTF-16LE-encoded captured test
log committed as a historical audit artifact (#121). The file hasn't
changed since the last green run on dev, so this is hook-environment
drift on the runner, not a content change.

Exclude docs/audit/ from the prettier hook: these are quarantined
historical artifacts and letting prettier rewrite a UTF-16 test log
would corrupt it. Verified pre-commit run --all-files passes locally.

Author: sidmohan0

.pre-commit-config.yaml

@@ -36,6 +36,7 @@ repos:
         exclude: |
           (?x)^(
             .venv|
+            docs/audit/.*|
             .*\.github/workflows/.*\.ya?ml$
           )$