Fix glob pattern for markdown files in paths-filter

The pattern `!**.md` doesn't correctly match markdown files in subdirectories. Changed to `!**/*.md` to properly exclude all .md files at any depth.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: blaginin

.github/workflows/rust.yml

@@ -49,7 +49,7 @@ jobs:
           filters: |
             code:
               - '**'
-              - '!**.md'
+              - '!**/*.md'
               - '!docs/**'
               - '!.github/ISSUE_TEMPLATE/**'
               - '!.github/pull_request_template.md'