feat(editor): add --summary-dir bulk content inventory

Recursively walks a directory, identifies every file by 4-byte
magic, and reports per-format file count, total entries, and
bytes. Useful for content audits ("how many cinematics did
this asset bundle ship?") and for tracking migration progress
("what fraction of zones still lack a holiday catalog?").

Also extracts the format-magic table out of cli_info_magic.cpp
into a shared cli_format_table.{hpp,cpp} so --info-magic and
--summary-dir reuse the same source of truth — adding a new
format now updates one row in one file instead of two. Both
flags use the standard catalog header (magic + version + name
+ entryCount) for catalog formats; asset/world formats are
counted but report 0 entries since their headers differ.

Supports --json variant for tooling integration.

tools/editor/cli_arg_required.cpp

@@ -134,7 +134,7 @@ const char* const kArgRequired[] = {
     "--gen-liquids", "--gen-liquids-magical", "--gen-liquids-hazardous",
     "--info-wliq", "--validate-wliq",
     "--export-wliq-json", "--import-wliq-json",
-    "--info-magic",
+    "--info-magic", "--summary-dir",
     "--gen-animations", "--gen-animations-combat", "--gen-animations-movement",
     "--info-wani", "--validate-wani",
     "--export-wani-json", "--import-wani-json",