feat(editor): add --bulk-validate to run every format's validator across a tree

Recursively walks a directory, peeks each file's 4-byte magic to
identify the format, derives the per-format --validate-X flag
from the format table's --info-X entry, and invokes that
validator as a subprocess for each file. Reports total / passed
/ failed / skipped counts and lists the failure paths with their
exit codes; returns exit 1 if any failure is found.

For each failure it prints the exact follow-up command needed to
reproduce the detailed error message, so the user doesn't have
to remember which validator goes with which extension. Asset-
style formats with no validator (.wom / .wob / .whm world
geometry) are counted in the "skipped" bucket but don't fail
the run.

Composes with the existing audit/fix tooling:
  --audit-tree dir          # find header-level breakage
  --magic-fix dir --apply   # auto-fix ext/magic mismatches
  --bulk-validate dir       # run every per-format validator
  # then re-run --validate-X on individual failures for detail

This is the 12th cross-format utility — depth-checking that
catches per-format semantic errors (duplicate ids, invalid
enums, contradictory flag combos, dangling cross-refs) that
--audit-tree's header-only scan can't see. CLI flag count
950 -> 951.

tools/editor/cli_arg_required.cpp

@@ -137,7 +137,7 @@ const char* const kArgRequired[] = {
     "--info-magic", "--summary-dir", "--rename-by-magic",
     "--bulk-rename-by-magic", "--touch-tree", "--tree-summary-md",
     "--catalog-grep", "--diff-headers", "--audit-tree",
-    "--magic-fix",
+    "--magic-fix", "--bulk-validate",
     "--gen-animations", "--gen-animations-combat", "--gen-animations-movement",
     "--info-wani", "--validate-wani",
     "--export-wani-json", "--import-wani-json",