fix: launch standalone Pi children directly

src/runs/shared/pi-spawn.ts

@@ -70,6 +70,11 @@ function normalizePath(filePath: string): string {
 	return path.isAbsolute(filePath) ? filePath : path.resolve(filePath);
 }
 
+function isStandalonePiExecutable(execPath: string): boolean {
+	const executableName = execPath.split(/[\\/]/).pop();
+	return /^pi(?:\.exe)?$/i.test(executableName ?? "");
+}
+
 export function resolvePiCliScript(
 	deps: PiSpawnDeps = {},
 ): string | undefined {
@@ -141,10 +146,15 @@ export function getPiSpawnCommand(
 		return { command: piBinary, args };
 	}
 
+	const execPath = deps.execPath ?? process.execPath;
+	if (isStandalonePiExecutable(execPath)) {
+		return { command: execPath, args };
+	}
+
 	const piCliPath = resolvePiCliScript(deps);
 	if (piCliPath) {
 		return {
-			command: deps.execPath ?? process.execPath,
+			command: execPath,
 			args: [piCliPath, ...args],
 		};
 	}

test/unit/pi-spawn.test.ts

@@ -73,6 +73,32 @@ describe("getPiSpawnCommand", () => {
 		assert.deepEqual(result, { command: "pi", args });
 	});
 
+	for (const [platform, execPath] of [
+		["darwin", "/opt/pi/pi"],
+		["win32", "C:\\Program Files\\Pi\\pi.exe"],
+	] as const) {
+		it(`uses the standalone Pi executable directly on ${platform}`, () => {
+			const packageJsonPath = "/opt/pi-package/package.json";
+			const cliPath = path.resolve(
+				path.dirname(packageJsonPath),
+				"dist/cli.js",
+			);
+			const deps = makeDeps({
+				platform,
+				execPath,
+				argv1: "/missing/host.js",
+				packageJsonPath,
+				packageJsonContent: JSON.stringify({ bin: { pi: "dist/cli.js" } }),
+				existing: [packageJsonPath, cliPath],
+			});
+			const args = ["--mode", "json", "-p", "Task: review diff"];
+			assert.deepEqual(getPiSpawnCommand(args, deps), {
+				command: execPath,
+				args,
+			});
+		});
+	}
+
 	for (const platform of ["darwin", "linux", "win32"] as const) {
 		it(`uses node + argv1 on ${platform} when argv1 belongs to the Pi package`, () => {
 			const tempDir = fs.mkdtempSync(