Document soundbank findings

docs/reverse-engineering/findings.md

@@ -68,6 +68,10 @@ Conclusion: approach A works end-to-end in-game. Use >= 30 s probes for the intr
     6 channels work at <= 32 kHz (uncoupled, like Wwise). The encoder falls back to 32 kHz automatically.
 15. Channel order for > 2 channels: the bitstream order equals the array order given to libsndfile; whether the game
     expects WAVEFORMATEX order (FL FR FC LFE BL BR) is unverified (identical-channel probes were used).
+16. (2026-10-09) The WADs hold only streamed audio. About 15,800 more sounds (footsteps, foley, combat, weapons,
+    UI, grunts) are in-memory WEMs inside soundbanks: 65 loose `SFX\*.bnk` (1,117) and 3,340 banks embedded in
+    the `.upk` packages (15,641; many banks copied into several packages). None are in the catalog; the WAD
+    side is complete. Inventory, layout and editing consequences: `docs/formats/banks.md`.
 
 ## Old path -> new path
 `scripts/harness.py` -> `ackit verify --ingame` (ackit/verify/ingame.py); `scripts/validate_builder.py` ->