Add HDR tonemap brightness slider

The engine applies mat_monitorgamma (SDL receives changing ramp midpoints),
but Wayland/XWayland compositors discard the window gamma ramp, so the gamma
slider has no visible effect there. Add an in-engine brightness control that
does not depend on the window system: mat_force_tonemap_scale, exposed as
"HDR brightness" (x10, 0 = automatic). Drop the temporary SDL gamma ramp
diagnostic.

1 files changed, 9 insertions, 8 deletions

diff --git a/CONTEXT.md b/CONTEXT.md
index fc73214..e0af84a 100644
--- a/CONTEXT.md
+++ b/CONTEXT.md
@@ -241,14 +241,15 @@ vocabulary / decisions.
   `ClientCmd` when their slider changes. Gamma is stored as x10
   (`[view] gamma=22` = 2.2) and the slider stops at 26 because the engine
   clamps `mat_monitorgamma` at 2.6. The value is read back through
-  `ICvar::FindVar` on the next tick (ClientCmd is queued) and logged
-  (`view: gamma request ..., cvar reports ...`) to distinguish a rejected
-  command from an OS gamma ramp the compositor ignores. `SDL_SetWindowGammaRamp`
-  is also interposed (first 12 calls log `gamma: SDL_SetWindowGammaRamp
-  mid=...`) to see whether the engine ever pushes a ramp after the slider
-  moves; if it does and the screen does not change, the compositor is
-  discarding it. Both live in the always-on
-  `Camera / display` card (`[view] fov/vmfov/gamma`).
+  `ICvar::FindVar` on the next tick (ClientCmd is queued) and logged. The
+  engine does apply the ramp (`SDL_SetWindowGammaRamp` was called with
+  changing midpoints), but a Wayland/XWayland compositor discards it, so on
+  this setup the slider has no visible effect.
+- `HDR brightness` (`[view] tonemap`, x10, 0 = automatic) sets
+  `mat_force_tonemap_scale`. This is in-engine tonemapping for HDR maps and
+  does not depend on the window system applying a gamma ramp; 10 = 1.0.
+  Both live in the always-on `Camera / display` card
+  (`[view] fov/vmfov/gamma/tonemap`).
 
 ## Map transitions