feat: warn about non-import references to moved files

The import graph only rewrites import/export-from/require. Files are
also named from markdown links, package.json fields, jest.mock strings
and tsconfig file lists, and a move that dangles those must not pass
silently. mv now scans text formats plus source strings for the moved
paths, module names and old specifier forms (word-boundary matched,
lockfiles/hidden dirs skipped) and reports each occurrence once per
line on stderr and as non_import_refs[] in --json (dry-run included).
References are never edited; exit codes are unchanged.

Also moves normalize_scope into Index (its only consumer) and the
Change/ChangedFile JSON structs into output where they are built, to
stay inside the 250-line-per-file budget.

README.md

@@ -60,6 +60,9 @@ jmove mv src/foo.ts src/bar/foo.ts --no-git
 # Move a whole directory: every file relocates, every importer follows
 jmove mv src/utils src/helpers
 
+# Moves also warn (never edit) about references the import graph cannot
+# see: markdown links, package.json fields, jest.mock strings
+
 # Java: jmove updates `package`, all `import`s and moves the file
 jmove mv src/com/example/utils/Parser.java src/com/example/core/Parser.java