World: add Fullbright visual feature

- New Visuals card with the usual Active + Bind; default off. Unbound+Active
  is always-on, a bind makes it hold-to-brighten.
- Resolve VEngineCvar004 and set mat_fullbright 1/0 through FindVar (slot 12)
  and ConVar::SetValue(int) (slot 11), bypassing the console cheat gate.
  Fall back to ClientCmd if the cvar interface is unavailable.
- Reapply after map loads/respawns and persist [fullbright] active/bind.
- Log on/off; show an error toast if the cvar cannot be applied.

1 files changed, 14 insertions, 0 deletions

diff --git a/CONTEXT.md b/CONTEXT.md
index 922ea98..283784f 100644
--- a/CONTEXT.md
+++ b/CONTEXT.md
@@ -269,6 +269,20 @@ vocabulary / decisions.
   assist deliberately writes only `m_vecAbsVelocity`; `SetAbsVelocity` syncs
   `m_vecVelocity` after the command.
 
+## World transformations
+
+### Fullbright
+
+- Visuals card with the usual Active + Bind. Unbound and Active means always
+  on; a bind makes it a hold-to-brighten key.
+- Applies the client `mat_fullbright` cvar to 1/0 through `VEngineCvar004`
+  (`FindVar` slot 12, `ConVar::SetValue(int)` slot 11), which bypasses the
+  console cheat gate. No server-side writes.
+- Re-applied after map loads/respawns (`fullbright_invalidate` on local entity
+  change) and saved as `[fullbright] active/bind`.
+- `fullbright: on/off` is logged; a missing cvar interface raises an error
+  toast instead of failing silently.
+
 ## Logging
 
 - `/tmp/hl2hake.log` is opened once at startup with `"w"` (so it only contains