Support @parcel/watcher as the watcher alternative

[nachocodoner]

Continues: #13657 and #13698

This PR continues the optimizations after switching to the SWC transpiler and dropping legacy compilation. It focuses on refactoring the file watchers used by Meteor, replacing them with a modern, native, and cross-platform tool: @parcel/watcher.

The change was suggested by @zodern. After reviewing the involved code, I found that Meteor used two libraries: Pathwatcher on Linux and vscode-NSFW on Windows/macOS. On Windows and macOS, Meteor enabled a single recursive watcher per directory using vscode-nsfw, efficiently covering whole trees. On Linux, recursive watchers weren’t available, and adding one per subdirectory would overload the system. To avoid that, Meteor used `pathwatcher, watching files and some directories individually. This added up to 5 seconds of delay in Linux when reacting to file changes, especially for new files.

The @parcel/watcher library offers a modern solution for recursive watching across platforms. It uses native backends: FSEvents (macOS), inotify or Watchman (Linux), and the Windows API. All through a unified interface. It supports recursive watching on all platforms, which is the key improvement here.

Results can be seen using METEOR_MONITOR_PROCESS=true in meteor profile. This outputs the full profile process. The “Meteor(Total)” time shows only what the internal profiler sees, not including watcher reaction time. The new “Meteor(Progress)” output includes delays like startup wait and file change reactions. This metric helps confirm the improvements in this PR. See the next profiles for reference:

The results got from a specific machine using fredmaiaarantes/simpletasks in a Linux-like OS

It seems to have improved the prepareProjectForBuild phase, likely because it involves setting up file watching. There's also a slight improvement in build and rebuild times. In some profiles, the safeWatcher.watch process appears as well.

This still needs more testing across all OS, but results so far look good.

---

• Investigate why ./meteor --get-ready fails; possible memory leak or limit with @parcel/watcher?
  • Apps tested locally worked well without issues.
• Ensure to mark a path as being subscribed beforehand to avoid parallel repeated subscriptions to the same folder context
  • Any gain out of this change?
• Remove LRU on file replacement since finally was not needed to fix an issue
• Fix tests affected by file watcher replacement

[netlify]

✅ Deploy Preview for v3-meteor-api-docs canceled.

Name	Link
🔨 Latest commit	c2dcae2
🔍 Latest deploy log	https://app.netlify.com/sites/v3-meteor-api-docs/deploys/6808c496e9593e0008d26e34

[nachocodoner]

Finally! This branch is ready to merge into 3.3. Next, I’ll test it more thoroughly across OS with all other changes in place.