ci(workflow-linter): scope uses: grep to require leading whitespace (#9)

The in-tree workflow-linter.yml ran `grep -rn "uses:"` across
workflow files, which matched its own comment lines (`# Pattern:
uses: ...`) and shell command lines, causing a self-referential
false positive.

Fix: require leading whitespace before `uses:` (matches
standards/governance-reusable.yml line 640 pattern).

Author: hyperpolymath

.github/workflows/workflow-linter.yml

@@ -63,7 +63,7 @@ jobs:
           echo "=== Checking Action Pinning ==="
           # Find any uses: lines that don't have @SHA format
           # Pattern: uses: owner/repo@<40-char-hex>
-          unpinned=$(grep -rn "uses:" .github/workflows/ | \
+          unpinned=$(grep -rnE "^[[:space:]]+uses:" .github/workflows/ | \
             grep -v "@[a-f0-9]\{40\}" | \
             grep -v "uses: \./\|uses: docker://\|uses: actions/github-script" || true)