Decide whether the other screens join in on workspaces

GNOME's Multitasking panel asked one workspace question worth reproducing, and
it is not which workspace goes on which screen. It is whether the second screen
participates at all: workspaces on the primary display only, or each screen with
its own. Ten rows of per-workspace assignment would be more powerful and worse.

Off is Hyprland's own behaviour and emits nothing. On pins workspaces 1 to 10 --
however many ALT+1..ALT+0 actually reach, read from keybinds.lua rather than
written down twice -- to whichever output is recorded as primary. With no
primary recorded, nothing is pinned: guessing one would move every workspace
onto whichever output happened to sort first, and this machine is in exactly
that state.

Applying is a reload, which is the part that shaped the design. Hyprland reads
workspace rules at config time and will not remove one afterwards -- a rule
written with an empty monitor keeps its old binding, which was checked rather
than assumed. Only a reload clears them, so the config is the only honest source
and the page cannot pretend a change has landed before one happens. Hence a
service that reads `hyprctl workspacerules` back rather than inferring success
from having written the preference, and a Reload row that exists only while the
two disagree.

Verified end to end against the live compositor and put back: off emits nothing,
on emits ten rules naming the primary, and turning it off clears them. The
settings file came back byte-identical.

Claude-Session: https://claude.ai/code/session_01Q84axqUE5inJhf5Jz9CFy1

README.md

@@ -99,7 +99,7 @@ docs/           Settings reference, and the design specs behind the work
 
 ## Tests
 
-128 of them, under `tests/`. Run the lot, or a subset by pattern:
+129 of them, under `tests/`. Run the lot, or a subset by pattern:
 
 ```sh
 panama test           # everything