fix(cli): doctor shows platform-correct install hints

[Dylanwooo]

Summary

hyperframes doctor shipped two bugs that misled non-Debian-Linux and Windows users:

1. Wrong FFmpeg install hint. When FFmpeg was missing, the hint was hardcoded as sudo apt install ffmpeg for every non-macOS platform. Windows users saw an apt command that doesn't exist on their system; Red Hat / Arch users got the wrong package manager.

2. FFprobe check broken on Windows. checkFFprobe called which ffprobe via execSync. which isn't a command on Windows (cmd uses where), so the check always reported "Not found" even when ffprobe was on PATH.

Fix

• checkFFmpeg now uses getFFmpegInstallHint() — the helper already exists in browser/ffmpeg.ts, already handles darwin / linux / win32 correctly, and is already used by render.ts. Just reuse it here.
• checkFFprobe now runs ffprobe -version directly instead of shelling out to which. This works on every platform where ffprobe is resolvable on PATH, and surfaces the version string in the same style as the FFmpeg check.
• The "not found" hint for ffprobe now falls through to the same platform-aware ffmpeg install hint (they ship together).

Before / After

Before (on Windows, ffprobe present):

✗ FFprobe    Not found
             Installed with ffmpeg

After:

✓ FFprobe    ffprobe version 8.1 Copyright (c) 2007-2026 …

Before (on Windows, FFmpeg missing):

✗ FFmpeg     Not found
             sudo apt install ffmpeg      ← wrong OS

After:

✗ FFmpeg     Not found
             https://ffmpeg.org/download.html

Test plan

• bunx oxlint packages/cli/src/commands/doctor.ts — clean
• bunx oxfmt --check packages/cli/src/commands/doctor.ts — clean
• Pre-commit typecheck hook passes
• bunx tsx packages/cli/src/cli.ts doctor runs locally on macOS — FFprobe now reports version instead of path, all other behavior unchanged

Notes

Scope intentionally kept small. findFFmpeg() in browser/ffmpeg.ts still uses which ffmpeg which has the same Windows issue — happy to fix in a follow-up PR if the maintainers want it, but it has a wider blast radius (used by render.ts too) so I left it out of this one.

[jrusso1020]

Thanks for the clean fix and the thorough write-up! The before/after examples and the scoping note made this really easy to review.

Approving as-is. This is a strict improvement: Windows users go from a wrong hint + broken ffprobe check to correct hints + a working check, and reusing getFFmpegInstallHint() is exactly the right move.

Good call leaving findFFmpeg() out — the which issue there has a wider blast radius (render.ts depends on it too) and deserves its own PR. I'll open follow-up issues for that one, plus one for making the Linux install hint distro-aware (the helper still returns sudo apt install ffmpeg for all Linux, so Arch/RHEL folks get the wrong package manager — not something to fix here).

Appreciate the contribution!