fix(core,fuse,cli,gui): say when an upgrade left the old daemon running

A package upgrade replaces the binaries but does not restart the user
service, so the daemon keeps the old release and its bugs until the next
login. On 3.2.0 the reporter of #33 still saw "Couldn't sync Documents:
read .../snapshots/37: Permission denied", which only a daemon older than
3.2.0 can produce: since then the scan leaves an unreadable subfolder out
and only an unreadable sync root fails the pass (B206).

The daemon now reports its release in Status; one from before the field
omits it, which reads as older. When the daemon is older than the
front-end, the tray says "Update not finished - restart Proton Drive" and
offers a restart, the sync card shows "Restart to finish updating" with a
Restart button, and pdfs status and pdfs diagnose print the systemctl
command. A newer daemon is not flagged, since then the front-end is the
stale one.

Refs #33

docs/BUGS.md

@@ -100,6 +100,7 @@ a live account since.
 
 | Entry | Title |
 |---|---|
+| [B206](#b206--an-upgrade-leaves-the-old-daemon-running-and-nothing-says-so) | An upgrade leaves the old daemon running, and nothing says so |
 | [B205](#b205--a-photo-upload-the-sdk-refuses-says-youre-offline) | A photo upload the SDK refuses says "You're offline" |
 | [B204](#b204--a-write-over-a-partial-edit-whose-base-was-never-read-fails-with-eio) | A write over a partial edit whose base was never read fails with `EIO` |
 | [B203](#b203--pdfs-unlock-leaves-a-running-daemon-a-spent-refresh-token) | `pdfs unlock` leaves a running daemon a spent refresh token |
@@ -308,6 +309,37 @@ a live account since.
 
 Newest first.
 
+### B206 — An upgrade leaves the old daemon running, and nothing says so
+
+**Status:** Fixed, not verified live
+**Found:** 2026-10-11, issue [#33](https://github.com/narrrl/proton-drive-linux/issues/33). On
+3.2.0 the reporter still saw `Couldn't sync Documents: Read …/snapshots/37: Permission denied`,
+the B196 failure 3.2.0 fixed. Since 3.2.0 the scan leaves an unreadable subfolder out and
+`walk_local_dir` can only fail the pass on the sync root, so that message comes from a daemon
+older than 3.2.0.
+**Where:** `Response::Status` and `daemon_outdated` in `crates/pdfs-core/src/control.rs`;
+`status_response` in `crates/pdfs-fuse/src/control.rs`; the tray in `crates/pdfs-gui/src/main.rs`;
+the sync card in `crates/pdfs-gui/src/app/pages/status.rs`; `pdfs status` and `pdfs diagnose`
+
+**Repro:** With the service running, install a newer package, then open the app.
+
+**Cause.** A package upgrade replaces the binaries but does not restart the user service, so the
+running daemon keeps the old release and its bugs until the next login or a manual restart. The
+app, the tray and the CLI start from the new binaries and could not tell, so they described the
+new release while the old one did the work.
+
+**Fix.** The daemon reports its release in `Status`. A daemon from before the field omits it,
+which reads as older. When the daemon is older than the front-end, the tray says "Update not
+finished — restart Proton Drive" with a Restart Proton Drive item, the sync card says "Restart to
+finish updating" with a Restart button, and `pdfs status` and `pdfs diagnose` print the
+`systemctl --user restart proton-drive` command. A newer daemon is not flagged: then the
+front-end is the stale one, and restarting the service would not help.
+
+**Test:** `control::tests::only_an_older_daemon_is_outdated`;
+`tests::a_daemon_older_than_the_tray_needs_a_restart` in `pdfs-tray`.
+
+---
+
 ### B205 — A photo upload the SDK refuses says "You're offline"
 
 **Status:** Fixed, not verified live