feat(editor): add WSCT (Spell Cast Time Index) open catalog format

Companion to WSRG: open replacement for SpellCastTimes.dbc plus
the per-spell castTime fields in Spell.dbc. Defines categorical
cast-time buckets (Instant 0ms / FastCast 1s / MediumCast 1.5s /
LongCast 3s) that thousands of spells reference instead of each
embedding their own ms count. Together WSRG and WSCT let the
spell engine resolve "Frostbolt's range bucket = id 3" and
"Frostbolt's cast time bucket = id 5" with two table reads
instead of duplicating per-rank data.

Cast time can scale with character level via perLevelMs (a rank-1
spell at 1000ms can grow to 2200ms at lvl 60), then the bucket
result is clamped to [minCastMs, maxCastMs] before haste is
applied. resolveAtLevel() does the math for engine consumers.

Three preset emitters: --gen-sct (4 baseline buckets),
--gen-sct-channel (3 channeled-spell durations), --gen-sct-ramp
(4 level-scaled buckets with non-zero perLevelMs). Validation
catches negative baseCastMs, min>max, duplicate ids, warns on
Instant kind with non-zero base (cast bar would still show), and
errors on Channel kind with zero base (would tick once and end).

Wired through the cross-format table; WSCT appears automatically
in all 9 cross-format utilities. Format count 68 -> 69; CLI flag
count 892 -> 897.

tools/editor/cli_arg_required.cpp

@@ -209,6 +209,8 @@ const char* const kArgRequired[] = {
     "--gen-srg", "--gen-srg-ranged", "--gen-srg-friendly",
     "--info-wsrg", "--validate-wsrg",
     "--export-wsrg-json", "--import-wsrg-json",
+    "--gen-sct", "--gen-sct-channel", "--gen-sct-ramp",
+    "--info-wsct", "--validate-wsct",
     "--gen-weather-temperate", "--gen-weather-arctic",
     "--gen-weather-desert", "--gen-weather-stormy",
     "--gen-zone-atmosphere",