feat(editor): add --magic-fix to auto-rename files to canonical extension

Natural follow-up to --audit-tree: when that utility flags
ext-mismatch or magic-no-ext issues, --magic-fix proposes (and
optionally applies) the renames that resolve them. Walks a
directory recursively, reads each file's 4-byte magic, looks it
up in the format table, and renames to the canonical extension
when the current extension doesn't match (or is absent).

Defaults to dry-run for safety — prints the proposed renames so
they can be reviewed first; pass --apply to commit them. Refuses
to clobber existing files: when the target path already exists
(e.g. foo.wsct + foo.wsrg both with WSRG magic), the rename is
flagged as a collision and skipped, leaving both files in place
for manual resolution. Returns exit 1 if any proposals exist (in
dry-run) or any collisions are skipped (in apply), so it composes
into shell pipelines.

JSON sidecar via --json. Suggested workflow:
  --audit-tree dir          # find what's broken
  --magic-fix dir           # preview the auto-fixes
  --magic-fix dir --apply   # commit them
  --audit-tree dir          # confirm clean

CLI flag count 921 -> 922.

tools/editor/cli_help.cpp

@@ -1367,6 +1367,8 @@ void printUsage(const char* argv0) {
     std::printf("                         Compare two .w* files at the standard catalog header level (magic / version / name / entry count / file size). Exit 1 if any field differs\n");
     std::printf("  --audit-tree <dir> [--json]\n");
     std::printf("                         Walk directory recursively and flag corrupted/misnamed Wowee files: too-small, unknown-magic, ext/magic mismatch, magic-without-ext, truncated headers. Exit 1 on any issue\n");
+    std::printf("  --magic-fix <dir> [--apply] [--json]\n");
+    std::printf("                         Auto-rename files whose extension doesn't match their magic to the canonical extension. Default is dry-run; pass --apply to commit. Skips collisions where the target already exists. Natural follow-up to --audit-tree\n");
     std::printf("  --gen-animations <wani-base> [name]\n");
     std::printf("                         Emit .wani starter: 5 essential animations (Stand / Walk / Run / Death / AttackUnarmed) with fallback chains\n");
     std::printf("  --gen-animations-combat <wani-base> [name]\n");