Write the manual for the person using the desktop

docs/ is engineering artifacts -- design specs, plans, an upstream
ledger -- and none of it is written for the person who has to live
here. Five chapters that are: coming from another desktop, the
keyboard, windows and workspaces, when something breaks, and making it
yours.

Rendered inside Settings rather than opened in a browser, so a chapter
that says "the Displays page reverts after fifteen seconds" is one
click from the Displays page. Qt's markdown renderer does the work;
one chapter per Text, because Text has an implicit texture size limit
and a document long enough to hit it goes blank rather than
complaining.

The chapters live beside the shell in manual/ rather than at the
repository root, which departs from the plan. The reason is the path:
the shell finds them through Quickshell.shellDir, which is correct
wherever the repository is, whereas walking upward out of the shell
directory is only correct by accident. The contract fails that pattern
if it comes back.

The contract also pins the set both ways -- every chapter listed
exists, every chapter that exists is listed -- because a renamed file
shows an error card where a chapter should be, which reads as a broken
manual rather than as a moved file.

config/dot/quickshell/manual/02-the-keyboard.md

@@ -0,0 +1,46 @@
+# The keyboard
+
+Press `Super + /` at any time to see every shortcut this machine has. That
+list is generated from the live keymap, so it is never out of date, and it
+includes anything you have rebound.
+
+This chapter is the shape behind that list, which is the part worth learning
+once.
+
+## Three modifiers, three jobs
+
+| Modifier | Acts on |
+|---|---|
+| `Super` | The window you are looking at |
+| `Alt` | Workspaces |
+| `Super + Ctrl` | The layout itself: splitting, floating, swapping |
+
+Almost every shortcut follows from this. `Super + H` moves focus left.
+`Alt + H` moves to the workspace on the left. `Super + Ctrl + H` swaps the
+window leftward in the layout.
+
+## Directions
+
+`H`, `J`, `K`, `L` mean left, down, up, right, as they do in vim. The arrow
+keys work everywhere the letters do, so you never have to learn them if you
+would rather not.
+
+Add `Shift` to move the window rather than the focus. `Super + Shift + L`
+takes the current window and moves it to the right.
+
+## The handful worth memorising first
+
+| Keys | What it does |
+|---|---|
+| `Super + Space` | Find and open anything |
+| `Super + T` | Terminal |
+| `Super + Q` | Close the window |
+| `Super + backtick` | Every window, every workspace |
+| `Super + I` | Settings |
+| `Super + /` | Every other shortcut |
+
+## Changing them
+
+Settings has a Shortcuts page listing every bind, each of which can be
+reassigned. A rebind moves the shortcut and cannot change what it does, so
+there is no way to make a key do something unexpected by editing it.