Add parsers for RT3 language and engine type assets

docs/rehost-queue/format-inventory-2026-04-21.md

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+# RT3 Format Inventory (2026-04-21)
+
+This note preserves the current file-format inventory under `rt3_wineprefix/drive_c/rt3` and
+`rt3_wineprefix/drive_c/rt3_105`, so future queue work can distinguish parser gaps from ordinary
+generic media/support files.
+
+## Parsed Game-Native Families
+
+These formats already have checked loader or inspection support in the current repo:
+
+- `.gmp`, `.gms`, `.gmx`: SMP/map/save/sandbox container inspection and save-slice loading
+- `.pk4`: pack4 archive inspection and entry extraction
+- `.bca`, `.bty`: building-source inspection
+- `.cty`: cargo-type inspection
+- `.lng`: language-table inspection
+- `.car`, `.lco`, `.cgo`, `.cct`: engine-type inspection
+- `.imb`: inline resource-descriptor inspection
+- `.win`: window-resource inspection
+- `.exe`: campaign-oriented PE inspection for `RT3.exe`
+
+## RT3-Native Or RT3-Adjacent Unparsed Families
+
+These formats are present in-tree and look like future RE/parser candidates, but the repo does not
+yet have a dedicated structured parser for them:
+
+- `.105`: version-suffixed executable copies such as `RT3.exe.105`
+- `.dat`: opaque game-data blobs such as `emitters.dat`
+- `.g`: shader text sources
+- `.cfg`: engine/game configuration files
+
+## Generic Media And Support Families
+
+These files are present under the game trees, but they are generic media/resource/support formats
+rather than RT3-specific parser targets:
+
+- PE/DLL-style binaries: `.asi`, `.dll`, `.flt`, `.m3d`
+- media/resources: `.bik`, `.bmp`, `.cur`, `.dds`, `.ico`, `.mp3`, `.scc`, `.tga`, `.wav`
+- support/docs/scripts: `.asm`, `.bak`, `.bat`, `.c`, `.css`, `.html`, `.js`, `.json`, `.log`,
+  `.nsi`, `.pdf`, `.rtf`, `.txt`
+
+## Current Counts
+
+Normalized lowercase extension counts across both trees:
+
+- parsed game-native: `gmp 86`, `gms 8`, `gmx 21`, `pk4 55`, `bca 173`, `bty 390`, `cty 92`,
+  `lng 5`, `car 342`, `lco 170`, `cgo 74`, `cct 22`, `imb 2`, `win 3`
+- RT3-native or RT3-adjacent unparsed: `105 2`, `dat 5`, `g 10`, `cfg 4`
+
+The immediate queue consequence is narrow: `.gmx` is already a known parsed container family, so
+it belongs in local save-corpus scans by default. The remaining unparsed RT3-native families above
+are preserved here for future parser or RE passes, but they are not active queue heads today.