[BUG] Ctrl shortcuts broke system-wide until relogin #658

Summary

Once, on 0.15.0 (AppImage) / GNOME Wayland, Ctrl-based keyboard shortcuts
stopped working system-wide (not just in vocalinux's target apps) until I
logged out and back in. Hard to reproduce on demand, so filing this
separately from #657 as a lower-confidence report with a
possible mechanism, not a repeatable bug.

What happened

• Ctrl+A (select all) and Ctrl+V (paste) stopped registering — affected Telegram (Qt), Obsidian (Electron), Nautilus (GTK4).
• Mouse-based equivalents (drag-select, right-click paste) worked fine.
• Plain text typing was unaffected — characters weren't dropped, altered, or
  misinterpreted as shortcuts.
• Quitting/disabling vocalinux did not fix it — only logout/login did.
• After relogin, keyboard layout also seemed to stop influencing injected
  text at all (possibly related, possibly a side effect of the relogin
  resetting something else — unclear).

I don't have a reliable reproduction path for this one.

Possible mechanism (unconfirmed, from reading the code)

I first suspected vocalinux itself was holding an exclusive grab on an input
device, but that doesn't check out: neither evdev_backend.py nor
pynput_backend.py calls .grab()/EVIOCGRAB or pynput's suppress=True —
they only listen, they don't intercept.

A more concrete candidate is _inject_via_clipboard_paste() in
text_injector.py, which simulates Ctrl+V as a single ydotool key call
with a 3-second timeout:

_YDOTOOL_V1_CTRL_V = ["ydotool", "key", "29:1", "47:1", "47:0", "29:0"]
# 29 = LEFTCTRL, 47 = V — press Ctrl, press V, release V, release Ctrl
...
subprocess.run(cmd, check=True, stderr=subprocess.PIPE, text=True, timeout=3)
except (subprocess.CalledProcessError, subprocess.TimeoutExpired) as e:
    logger.warning(f"Paste simulation failed: {e}")

If ydotoold stalls and this hits the 3s timeout, the client process gets
killed mid-sequence. If the daemon had already applied 29:1 (Ctrl-down) to
its virtual uinput device before the client was killed, but never received
29:0 (Ctrl-up), the virtual Ctrl key could stay logically "held" on that
device — separate from the real keyboard. That would explain: real typing
unaffected (different device), mouse actions unaffected (not
modifier-dependent), Ctrl shortcuts broken system-wide (Mutter aggregates
modifier state across all input devices for global shortcuts), and only
logout fixing it (restarts the session's input stack, presumably including
ydotoold's uinput device — quitting vocalinux alone doesn't touch the
separate ydotoold process).

Not confirmed, just flagging a specific, checkable spot rather than "Mutter
broke." If it holds up, an explicit safety-net release (e.g. always send a
bare ydotool key 29:0 after a TimeoutExpired/CalledProcessError here)
would be a cheap mitigation regardless of the exact trigger.

If it happens again, I'll try to look into logs of Voca and gnome-shell.

Environment

• vocalinux 0.15.0, AppImage
• GNOME on Wayland
• Arch latest packages