Fix backfill usage output for checkpoint flag (#1721)

Author: Widthdom

src/CodeIndex/Cli/ConsoleUi.cs

@@ -62,7 +62,7 @@ private static readonly (string Command, string Usage)[] CommandUsageLines =
     [
         ("index", "cdidx index <projectPath> [--db <path>] [--rebuild] [--optimize] [--verbose] [--dry-run] [--force] [--quiet] [--json] [--memory-trace] [--duration-format <auto|seconds|hms>] [--max-file-bytes <bytes>] [--follow-symlinks <none|internal|all>] [--include-symbol-kind <kind>[,<kind>]] [--exclude-symbol-kind <kind>[,<kind>]] [--watch [--debounce <ms>]]"),
         ("hooks", "cdidx hooks <install|uninstall|status> [--project <path>] [--force] [--json]"),
-        ("backfill-fold", "cdidx backfill-fold [--db <path>] [--dry-run] [--json]"),
+        ("backfill-fold", "cdidx backfill-fold [--db <path>] [--dry-run] [--no-checkpoint] [--json]"),
         ("optimize", "cdidx optimize [--db <path>] [--json]"),
         ("vacuum", "cdidx vacuum [--db <path>] [--json]"),
         ("index-commits", "cdidx index <projectPath> --commits <id> [id ...] [--db <path>] [--verbose] [--dry-run] [--json] [--memory-trace] [--duration-format <auto|seconds|hms>] [--max-file-bytes <bytes>] [--include-symbol-kind <kind>[,<kind>]] [--exclude-symbol-kind <kind>[,<kind>]]"),