DEVX-118: fix: exclude .vale directory from lint_docs scanning

Third-party Vale style packages contain README.md files with code blocks
that don't specify a language, causing false positives in lint_docs.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

src/devx/ci/lint_docs.py

@@ -85,6 +85,7 @@ _EXCLUDE_DIRS = {
     ".pytest_cache",
     ".devin",
     ".terraform",
+    ".vale",
     "site-packages",
     "dist-info",
 }