Let the Dock choose an edge, choose its screens, and be dragged into order

Three things that were parked, and the reasons they were parked turned out to be
the useful part of doing them.

The Dock can sit on the left or the right as well as the bottom. Everything that
assumed the bottom edge is now asked which edge it is on: the anchors, the axis
that gets an implicit size, the sliver of input region that survives hiding, the
direction the body slides away in, and which side a tooltip opens towards. The
body was a Row and is a Grid, because one declaration then serves both
orientations -- Row and Column would each need their own children, and the
cross-axis anchors that centre items in a Row are the wrong axis in a Column.

Bottom is unchanged in every particular, and the settings default to it, so a
hot reload in the middle of this work left the running dock exactly where it
was.

One bug worth recording because static review would never have found it: a dock
spans the edge it lives on, which means anchoring BOTH ends of that edge. The
first side dock anchored top and left only, was free to collapse to its implicit
height, and came out one pixel tall. It parsed, it loaded, and it rendered
nothing. The contract measures the geometry rather than reading the source for
that reason, and was verified by putting the single-ended anchor back.

Per-screen is a list of names where empty means every screen, because a list is
what goes stale when a display is unplugged and "all" should not be spelled as
one. Turning off the last screen collapses to "all" rather than leaving no dock
anywhere and no obvious way back.

Pins can be dragged by a grip. The objection this file recorded for a long time
was real -- dragging inside a Flickable inside a scrolling page fails in a way
that reads as breakage -- and the answer is preventStealing on the grip, so the
page cannot claim a gesture that started there. The arrow buttons stay: they are
the keyboard-reachable path and a grip is not. The order is held locally during
the drag and written once on release, rather than rewriting settings.json for
every slot crossed.

Claude-Session: https://claude.ai/code/session_01BRvzt4H8XXLPVH5MyYdk9L

docs/settings.md

@@ -4,7 +4,7 @@
 Do not edit this file. Run `quickshell/scripts/panama-settings-docs`
 after changing the schema; a contract fails when this copy is stale.
 
-132 settings across 27 groups. 67 of them are applied to the compositor and confirmed by reading the value back.
+133 settings across 27 groups. 67 of them are applied to the compositor and confirmed by reading the value back.
 
 ## accessibility
 
@@ -66,6 +66,7 @@ Found on **Desktop & Dock**.
 | Setting | Default | What it does |
 |---|---|---|
 | **Automatically hide the Dock**<br>`dockAutohide` | true | Reveal it at the bottom edge when a workspace is occupied |
+| **Position**<br>`dockPosition` | bottom | Which edge the Dock lives on Choices: Bottom, Left, Right. |
 | **Icon size**<br>`dockIconSize` | 48 px | How large the Dock's application icons are drawn. Range 32–80. |
 | **Reveal delay**<br>`dockRevealDelayMs` | 0 ms | Zero reveals the Dock the instant the pointer reaches the edge. Range 0–1000. |
 | **Hide delay**<br>`dockHideDelayMs` | 250 ms | Prevents flicker when crossing between icons. Range 0–2000. |