feat: add laptop/display brightness modulation

programs/include/montauk/capabilities.h

@@ -38,6 +38,7 @@ namespace caps {
         {"log_read",      montauk::abi::CAP_LOG_READ},
         {"system_image",  montauk::abi::CAP_SYSTEM_IMAGE},
         {"compositor",    montauk::abi::CAP_COMPOSITOR},
+        {"brightness",    montauk::abi::CAP_BRIGHTNESS},
     };
 
     // Never implied by "all": each must be named explicitly in a grant.

programs/include/montauk/consent.h

@@ -31,10 +31,12 @@ namespace consent {
          "0:/os/icons/network-wired.svg"},
         {montauk::abi::CAP_SET_TIME,      "change the system clock and time zone",
          "0:/os/icons/preferences-system-time.svg"},
-        {montauk::abi::CAP_DISPLAY_ADMIN, "change the screen resolution and brightness",
+        {montauk::abi::CAP_DISPLAY_ADMIN, "change the screen resolution",
          "0:/os/icons/preferences-desktop-display.svg"},
         {montauk::abi::CAP_LOG_READ,      "read the system log, which can reveal what other apps and devices are doing",
          "0:/os/icons/utilities-log-viewer.svg"},
+        {montauk::abi::CAP_BRIGHTNESS,    "change the screen brightness",
+         "0:/os/icons/preferences-desktop-display.svg"},
     };
 
     // Fallback for a capability without its own icon.