fix: add nolint:errcheck comments for intentionally unchecked errors

Add //nolint:errcheck comments to intentionally unchecked error returns:

- defer X.Close() calls: errors from closing read-only resources, rows
  after iteration, files, response bodies, and gzip readers are not
  actionable and don't affect correctness

- defer tx.Rollback(): standard Go pattern where rollback after
  successful commit returns an error, which is expected behavior

- defer stmt.Close(): statements are closed with their transactions

- Cleanup operations: DeleteRevision on failure and os.RemoveAll for
  temp directories are best-effort cleanup

- HTTP response encoding: if JSON encoding fails at response time,
  there's nothing useful we can do

- Test/benchmark code: unchecked errors in test setup/cleanup where
  failures will surface through test assertions

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cmd/hm-options/main.go

@@ -191,7 +191,7 @@ func runServe(c *cli.Context) error {
 	if err != nil {
 		return fmt.Errorf("failed to open database: %w", err)
 	}
-	defer store.Close()
+	defer store.Close() //nolint:errcheck // cleanup on exit
 
 	if err := store.Initialize(ctx); err != nil {
 		return fmt.Errorf("failed to initialize database: %w", err)
@@ -234,7 +234,7 @@ func runIndex(c *cli.Context, revision string, indexFiles bool, force bool) erro
 	if err != nil {
 		return fmt.Errorf("failed to open database: %w", err)
 	}
-	defer store.Close()
+	defer store.Close() //nolint:errcheck // cleanup on exit
 
 	if err := store.Initialize(ctx); err != nil {
 		return fmt.Errorf("failed to initialize database: %w", err)
@@ -288,7 +288,7 @@ func runList(c *cli.Context) error {
 	if err != nil {
 		return fmt.Errorf("failed to open database: %w", err)
 	}
-	defer store.Close()
+	defer store.Close() //nolint:errcheck // cleanup on exit
 
 	if err := store.Initialize(ctx); err != nil {
 		return fmt.Errorf("failed to initialize database: %w", err)
@@ -325,7 +325,7 @@ func runSearch(c *cli.Context, query string) error {
 	if err != nil {
 		return fmt.Errorf("failed to open database: %w", err)
 	}
-	defer store.Close()
+	defer store.Close() //nolint:errcheck // cleanup on exit
 
 	if err := store.Initialize(ctx); err != nil {
 		return fmt.Errorf("failed to initialize database: %w", err)
@@ -397,7 +397,7 @@ func runGet(c *cli.Context, name string) error {
 	if err != nil {
 		return fmt.Errorf("failed to open database: %w", err)
 	}
-	defer store.Close()
+	defer store.Close() //nolint:errcheck // cleanup on exit
 
 	if err := store.Initialize(ctx); err != nil {
 		return fmt.Errorf("failed to initialize database: %w", err)
@@ -490,7 +490,7 @@ func runDelete(c *cli.Context, revision string) error {
 	if err != nil {
 		return fmt.Errorf("failed to open database: %w", err)
 	}
-	defer store.Close()
+	defer store.Close() //nolint:errcheck // cleanup on exit
 
 	if err := store.Initialize(ctx); err != nil {
 		return fmt.Errorf("failed to initialize database: %w", err)