fix: repair audit-full build and inventory errors

Fix bash 3.2 parser error on escaped space in collect-inventory.sh
(=~ ^require\ ]] -> [[:space:]]). Remove unused Go imports in
cmd/audit/main.go and internal/security/claude.go, and an unused
test variable in osv_test.go so go build and go vet pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GVbEgdgcC1w6qwSq3zC4kg

scripts/collect-inventory.sh

@@ -105,7 +105,7 @@ for go_mod in ~/go/src/*/go.mod ~/.config/*/go.mod /tmp/*/go.mod; do
     dir=$(dirname "$go_mod")
     if command -v go &> /dev/null; then
       while IFS= read -r line; do
-        if [[ "$line" =~ ^require\ ]]; then
+        if [[ "$line" =~ ^require[[:space:]] ]]; then
           continue
         fi
         if [ -z "$line" ] || [[ "$line" == ")" ]] || [[ "$line" =~ ^\/\/ ]]; then