feat(editor): add WMAT JSON round-trip (--export/--import-wmat-json)

Closes the editing loop on the item-material catalog: dump a
.wmat to JSON, hand-edit materialKind / weightCategory / foley /
impact sound bindings / material flags (e.g. swap a Hide entry
from Light to Medium weight, add IsBreakable to a wooden bow,
re-bind Plate's foley to a different WSND entry, mark a new
HolyForged variant), re-import to a byte-identical binary.

Three different field types each take dual int+name forms:
  - materialKind: int 0..11 OR "cloth"/"leather"/"mail"/"plate"/
    "wood"/"stone"/"metal"/"liquid"/"organic"/"crystal"/
    "ethereal"/"hide"
  - weightCategory: int 0..2 OR "light"/"medium"/"heavy"
  - materialFlags: int bitfield OR pipe-separated label string
    ("IsMagical|IsBreakable|IsHolyCharged"). Importer prefers
    int form when both present so unknown bits round-trip
    losslessly.

Verified byte-identical round-trip on all three presets
(armor / weapon / magical). CLI flag count 948 -> 950.

tools/editor/cli_arg_required.cpp

@@ -233,6 +233,7 @@ const char* const kArgRequired[] = {
     "--export-wcdf-json", "--import-wcdf-json",
     "--gen-mat", "--gen-mat-weapon", "--gen-mat-magical",
     "--info-wmat", "--validate-wmat",
+    "--export-wmat-json", "--import-wmat-json",
     "--gen-weather-temperate", "--gen-weather-arctic",
     "--gen-weather-desert", "--gen-weather-stormy",
     "--gen-zone-atmosphere",