fix(colors): only send terminal escape sequences to real terminals

[M7MMAD-OMAR]

Describe your changes

apply_anyterm writes the generated OSC palette into every /dev/pts/*.

Not every pty belongs to a terminal emulator. A process can hold one open
without using it as a controlling terminal, and on a setup with KDE components
installed — which the Fedora dependency set pulls in — kded6 does exactly
that. What lands there is not a recolour; it is a desktop notification whose
body is the raw escape sequence. That is what #3453 is reporting, with the
screenshot of colour codes in a notification popup.

Here, /dev/pts/2 is held by kded6 and has no controlling-terminal process,
while every real terminal's pty has one:

/dev/pts/2   controlling=[]              holders=[kded6]     <- notification
/dev/pts/8   controlling=[fish]          holders=[fish]
/dev/pts/9   controlling=[bash]          holders=[bash]

The same loop also leaks processes. Each write is a disowned cat redirected
into the pty, and on a pty nobody reads from, it never finishes. On this machine
71 of them had accumulated, one batch per wallpaper change.

The fix

Skip any pty that has no process using it as a controlling terminal. That is
exactly the property separating a terminal emulator's pty from one that is
merely held open, and it needs no allowlist of terminal names to maintain.

Measured on the same machine, per wallpaper change:

	before	after
leaked cat processes	3	0
notification from kded6	yes	no

Fixes #3453

Is it ready? Questions/feedback needed?

Ready. Tested on Fedora 44 with Hyprland 0.56.2 and quickshell-git 0.2.1;
open terminals still recolour on a wallpaper change.

Two notes:

• ps -t is in coreutils/procps and already assumed elsewhere in the repo, so
  this adds no dependency.
• The workaround in the issue thread filters with fuser + ps comm against a
  list of terminal names. The controlling-terminal check gets the same result
  without anyone having to keep that list current.