feat: add compositor capability

programs/include/montauk/capabilities.h

@@ -37,13 +37,18 @@ namespace caps {
         {"device_admin",  montauk::abi::CAP_DEVICE_ADMIN},
         {"log_read",      montauk::abi::CAP_LOG_READ},
         {"system_image",  montauk::abi::CAP_SYSTEM_IMAGE},
+        {"compositor",    montauk::abi::CAP_COMPOSITOR},
     };
 
+    // Never implied by "all": each must be named explicitly in a grant.
+    inline constexpr uint64_t EXPLICIT_ONLY =
+        montauk::abi::CAP_SYSTEM_IMAGE | montauk::abi::CAP_COMPOSITOR;
+
     inline uint64_t bit_for_name(const char* name) {
         if (name == nullptr || name[0] == '\0') return 0;
         // "all" means "everything this launcher may pass on".
         if (montauk::streq(name, "all"))
-            return montauk::abi::CAP_ALL & ~montauk::abi::CAP_SYSTEM_IMAGE;
+            return montauk::abi::CAP_ALL & ~EXPLICIT_ONLY;
         for (const auto& entry : NAMES) {
             if (montauk::streq(entry.name, name)) return entry.bit;
         }