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

internal/security/claude.go

@@ -3,7 +3,6 @@ package security
 import (
 	"encoding/json"
 	"fmt"
-	"os"
 	"os/exec"
 	"strings"
 )

internal/security/osv_test.go

@@ -72,7 +72,7 @@ func TestQueryOSVWithMockedServer(t *testing.T) {
 	// Note: In actual implementation, we'd need to inject the base URL
 	// For now, this test validates the response parsing logic
 	t.Run("parse_valid_response", func(t *testing.T) {
-		pkg := inventory.Package{
+		_ = inventory.Package{
 			Name:    "requests",
 			Version: "2.28.0",
 			Source:  "pip",