Polish Feynman harness and stabilize Pi web runtime

src/system/executables.ts

@@ -0,0 +1,46 @@
+import { spawnSync } from "node:child_process";
+import { existsSync } from "node:fs";
+
+export const PANDOC_FALLBACK_PATHS = [
+	"/opt/homebrew/bin/pandoc",
+	"/usr/local/bin/pandoc",
+];
+
+export const BREW_FALLBACK_PATHS = [
+	"/opt/homebrew/bin/brew",
+	"/usr/local/bin/brew",
+];
+
+export const BROWSER_FALLBACK_PATHS = [
+	"/Applications/Google Chrome.app/Contents/MacOS/Google Chrome",
+	"/Applications/Chromium.app/Contents/MacOS/Chromium",
+	"/Applications/Brave Browser.app/Contents/MacOS/Brave Browser",
+	"/Applications/Microsoft Edge.app/Contents/MacOS/Microsoft Edge",
+];
+
+export const MERMAID_FALLBACK_PATHS = [
+	"/opt/homebrew/bin/mmdc",
+	"/usr/local/bin/mmdc",
+];
+
+export function resolveExecutable(name: string, fallbackPaths: string[] = []): string | undefined {
+	for (const candidate of fallbackPaths) {
+		if (existsSync(candidate)) {
+			return candidate;
+		}
+	}
+
+	const result = spawnSync("sh", ["-lc", `command -v ${name}`], {
+		encoding: "utf8",
+		stdio: ["ignore", "pipe", "ignore"],
+	});
+
+	if (result.status === 0) {
+		const resolved = result.stdout.trim();
+		if (resolved) {
+			return resolved;
+		}
+	}
+
+	return undefined;
+}