When working with multiple windows, one agent worked in the external
hard drive's directory.
After finishing working on that external dir, I've closed the entire
window (the other one, unrelated, remained) only to discover I cannot
unmount the external hard drive.

Investigated, and seems that that manual `ref_count` is buggy — replaced
that with `WeakEntry` for both agent and ACP parts.
Also added leaked project logging into reliability.

Release Notes:

- Fixed projects leaking via agents panel