Refactor runner and installation scripts for improved functionality

- Removed the `--disable-hiprt` flag from the runner command, simplifying the rendering options for users.
- Updated the `jiggablend-runner` script and README to reflect the removal of the HIPRT control flag, enhancing clarity in usage instructions.
- Enhanced the installation script to provide clearer examples for running the jiggablend manager and runner, improving user experience during setup.
- Implemented a more robust GPU backend detection mechanism, allowing for better compatibility with various hardware configurations.

Makefile

@@ -27,7 +27,19 @@ cleanup: cleanup-manager cleanup-runner
 run: cleanup build init-test
 	@echo "Starting manager and runner in parallel..."
 	@echo "Press Ctrl+C to stop both..."
-	@trap 'kill $$MANAGER_PID $$RUNNER_PID 2>/dev/null; exit' INT TERM; \
+	@MANAGER_PID=""; RUNNER_PID=""; INTERRUPTED=0; \
+	cleanup() { \
+		exit_code=$$?; \
+		trap - INT TERM EXIT; \
+		if [ -n "$$RUNNER_PID" ]; then kill -TERM "$$RUNNER_PID" 2>/dev/null || true; fi; \
+		if [ -n "$$MANAGER_PID" ]; then kill -TERM "$$MANAGER_PID" 2>/dev/null || true; fi; \
+		if [ -n "$$MANAGER_PID$$RUNNER_PID" ]; then wait $$MANAGER_PID $$RUNNER_PID 2>/dev/null || true; fi; \
+		if [ "$$INTERRUPTED" -eq 1 ]; then exit 0; fi; \
+		exit $$exit_code; \
+	}; \
+	on_interrupt() { INTERRUPTED=1; cleanup; }; \
+	trap on_interrupt INT TERM; \
+	trap cleanup EXIT; \
 	bin/jiggablend manager -l manager.log & \
 	MANAGER_PID=$$!; \
 	sleep 2; \