Add fresh CMake/platform scaffolding, core engine, and SDL3 window

Platform folders, cmake target/option/platform detection, Linux and PSP
scripts and Docker setup, assert/util/thread/error/log/perf/time/console/
engine/display modules, and an SDL3 window cleared to red.

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

scripts/psp/install.sh

@@ -0,0 +1,30 @@
+#!/bin/bash
+# Installs the packages required to build Dusk for the PSP. The PSP toolchain
+# itself (pspdev) must already be installed; the pspdev/pspdev docker image
+# provides it.
+set -e
+
+SUDO=""
+if [ "$(id -u)" -ne 0 ]; then
+  SUDO="sudo"
+fi
+
+if command -v apk >/dev/null 2>&1; then
+  $SUDO apk add --no-cache git cmake make python3 py3-pip py3-dotenv
+elif command -v apt-get >/dev/null 2>&1; then
+  $SUDO apt-get update
+  $SUDO apt-get install -y git cmake make python3 python3-pip python3-dotenv
+elif command -v dnf >/dev/null 2>&1; then
+  $SUDO dnf install -y git cmake make python python3-dotenv
+elif command -v pacman >/dev/null 2>&1; then
+  $SUDO pacman -Sy --noconfirm --needed git cmake make python python-dotenv
+else
+  echo "Unsupported package manager; install dependencies manually." >&2
+  exit 1
+fi
+
+if [ -z "$PSPDEV" ] || ! command -v psp-cmake >/dev/null 2>&1; then
+  echo "pspdev toolchain not found. Install it from https://pspdev.github.io/" >&2
+  echo "and set PSPDEV, or use scripts/psp/build-docker.sh." >&2
+  exit 1
+fi