v2.0.15: Model initialization blocks indefinitely when launched via launchd (macOS LaunchAgent)

[murilotoneta-blip]

Bug description

Syncthing v2.0.15 ("Hafnium Hornet") fails to initialize the folder model when launched
via a macOS LaunchAgent (launchd). The Ready to synchronize log entry is never emitted,
and all model-dependent API endpoints (/rest/db/status) block indefinitely.

The same binary initializes in <1 second when launched from a terminal (pty context).

Reproduction

1. Any LaunchAgent plist (RunAtLoad: true) pointing to the syncthing binary
2. brew install syncthing && brew services start syncthing
   Both block forever.

Works fine:

nohup /Applications/Syncthing.app/Contents/Resources/syncthing/syncthing \
  --no-browser --no-restart &