fix(cli): detect missing Chrome libs & ffmpeg on Linux/WSL in doctor (#1841)

WSL first-render success (34.7%) is dominated by a downloaded chrome-headless-shell that launches into `libnss3.so: cannot open shared object file` — doctor/preflight only checked the binary exists, never that it can load its libraries.

- New linuxDeps.ts: /etc/os-release distro detection (Debian/Fedora/Arch/Alpine) + WSL detection, per-distro Chrome dep set, ldd-based shared-lib probe.
- preflight.checkChrome downgrades a found-but-unlaunchable Chrome to a render-blocking error with the exact per-distro install command.
- Distro-aware ffmpeg hints; launch failures converted to actionable guidance pointing at `hyperframes doctor` (skipped on ARM64).
- Detect + print remediation (no auto-install).

Render-reliability workstream P1-4. Success measured on PostHog dashboard 1783183.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/cli/src/browser/ffmpeg.ts

@@ -2,6 +2,7 @@
 import { execSync } from "node:child_process";
 import { existsSync } from "node:fs";
 import { resolve } from "node:path";
+import { detectLinuxDistro, ffmpegInstallCommand } from "./linuxDeps.js";
 
 export const FFMPEG_PATH_ENV = "HYPERFRAMES_FFMPEG_PATH";
 export const FFPROBE_PATH_ENV = "HYPERFRAMES_FFPROBE_PATH";
@@ -62,8 +63,12 @@ export function getFFmpegInstallHint(): string {
   switch (process.platform) {
     case "darwin":
       return "brew install ffmpeg";
-    case "linux":
-      return "sudo apt install ffmpeg";
+    case "linux": {
+      // Distro-aware so WSL/Fedora/Arch/Alpine users get a command that
+      // actually works instead of a Debian-only `apt` line.
+      const distro = detectLinuxDistro();
+      return ffmpegInstallCommand(distro.family);
+    }
     case "win32":
       return "Download the 64-bit Windows build from https://ffmpeg.org/download.html#build-windows and add its bin/ directory to PATH.";
     default: