Describe DLSS, FSR 3.1, frame generation, HDR and the build kit in the READMEs; name a null call's caller.

The README takes the name NX2navi as on GitHub and lists the new upscalers, frame generation, the HDR modes, the
higher resolutions and the shader preparation, and points to the build kit for installing. A crash calling address 0
now logs the return address on top of the stack and its module (it was inside sl.common.dll for Streamline).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/README-BuildKit.md

@@ -1,4 +1,4 @@
-# Ocarina Recomp build kit
+# NX2navi build kit
 
 This kit builds *The Legend of Zelda: Ocarina of Time* (Nintendo Switch 2, game version 1.1.1) as a native Windows
 program **on your PC, from your own copy of the game**. The kit contains no game code or data. Everything the build
@@ -34,7 +34,7 @@ writes (`ocarina.exe`, the RomFS image, the shader cache, your saves) comes from
    Answer `Y` when it asks. If MSYS2 is somewhere other than `C:\msys64`, add `--msys <folder>\ucrt64` to the build
    command.
 
-## Build (about 10 to 25 minutes, once)
+## Build (about 10 to 15 minutes, once)
 
 Unpack this kit anywhere, open a Command Prompt in its folder and run:
 
@@ -58,8 +58,13 @@ When it says `finished`, start `C:\Games\Ocarina\ocarina.exe`. You can delete `C
 ## Playing
 
 - **F1** opens the settings menu. Settings are saved in `nx2navi.ini` beside the game; saves go to `profile\`.
-- The first time a shader appears it is translated, which can stutter briefly; it is cached from then on. After an
-  update of the kit or your graphics driver, the next start shows "Preparing shaders" once.
+- Every shader was prepared during the build. After an update of your graphics driver, the next start shows
+  "Preparing shaders" once while the driver rebuilds them.
+- **Screen** in the menu has Upscaling (DLSS on NVIDIA RTX cards, FSR 3.1 on any card), Frame generation (FSR 3.1; it
+  needs DLSS or FSR 3.1 upscaling on), HDR (Native is the game's own HDR; turn HDR on in Windows first) and the
+  resolution. Those marked "after restart" take effect when the game starts again.
+- DLSS needs `nvngx_dlss.dll` from NVIDIA beside `ocarina.exe` (the kit does not include it); FSR 3.1's
+  `amd_fidelityfx_vk.dll` is copied there by the build.
 - Logs are in `logs\`. When reporting a problem, say where you were in the game and which graphics card you have, and
   attach `logs\nx2navi.log`. Never send game files.