Fix OptiScaler NGX routing and align marker polling defaults

- Explicitly route OptiScaler to d4r\nvngx.dll in release packages.

- Extract INI generation into a helper that preserves line endings
  and rejects missing or duplicate settings.

- Check NGX routing separately from file presence and return failure
  when the installation is incomplete or misconfigured.

- Add an optional OptiScaler patch for external DLSS backends while
  preserving AMD identity for FSR4, with matching launch guidance.

- Align portable and launcher marker polling defaults at 200 us.

- Log when d4r's model override replaces game or OptiScaler presets.

- Add configuration, package, routing and coexistence regression tests.

- Update installation documentation, add FSR/DLSS comparison videos
  and ignore local .tools artifacts.

Refs: #7, #14

packaging/d4r.ini

@@ -52,6 +52,8 @@ NativeFp8 = on
 MotionVectorDilation = 0
 ; Keep inputs and output in video memory. Input and output readiness waits use CPU sleeps.
 VramInterop = true
+; Microseconds between checks for the game's input marker (default 200; 0 yields).
+MarkerPollUs = 200
 LinearInputs = true
 ElideNgxSync = true
 ; Lets DLSS's last kernel write straight into the game's output buffer (DLSS 4 / K only). It takes