fix(daemon): propagate snapshot env to process.env for child processes

[heyalchang]

Summary

• Apply daemon.json snapshot env keys to process.env so child processes (yt-dlp, ffmpeg, deno, tesseract) inherit the correct PATH under launchd/systemd

Fixes #98

Problem

Under launchd, process.env.PATH is /usr/bin:/bin:/usr/sbin:/sbin. The daemon's merged env is used internally to find binaries, but spawnTracked() spawns child processes without passing env — so they inherit the minimal PATH.

This breaks yt-dlp 2025.11.12+ which needs deno for YouTube JS challenges when cookies are enabled, causing "Requested format is not available" on slide extraction.

Change

In src/daemon/cli.ts, after building the merged env, iterate the whitelisted snapshot keys from daemon.json and apply them to process.env:

for (const [key, value] of Object.entries(cfg.env)) {
  if (typeof value === "string") {
    process.env[key] = value;
  }
}

Only the keys from env-snapshot.ts (PATH, API keys, tool paths) are in cfg.env — no arbitrary env vars leak through.

Test plan

• pnpm -s build passes
• pnpm test — 272 passed, 0 failures
• Manual: summarize daemon restart → trigger slides from Chrome extension → verify slides: done in daemon.log

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