Tidy a branch and line nodes up (stage 9a)

The first small part of stage 9 (v1.1). <Space>= then m, c or g (the
user's pick: leader menus), or :tidy map|chart|grid, lays out the
cursor's branch while its top node stays put: a mind map puts each node
in the middle of its children (the user's pick), an org chart puts them
side by side below, and a grid makes a block of cards beside the node
(the user's pick), a card's own branch going along as a mind map. Every
node of the branch gets a place, folded away or not (the user's pick),
as one undo step, and the message says when the branch now covers nodes
outside it.

The lines follow the layouts: a parent whose children are all below it
sends its branches down to a shared bend, and a new child of it goes
beside the last one; a grid card behind another isn't joined by a line,
which would look like it joins the two cards.

In visual mode, <Space>a then h, l, k, j or c lines the selection up on
the box around it, each node bringing its branch along, and : opens the
command line on the selection: :align and :tidy take it, and so do
:color, :border, :style, :tag and :fold, as one undo step. The layouts
are pure functions in view::canvas::arrange, applied as one
EditOp::Reposition. Layout and Side moved from the parser to the model
so keys can name them.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

README.md

@@ -88,6 +88,8 @@ The plan for the everyday keys (all of them are in DESIGN.md):
 | `K`               | the body in a card beside the node (`i` edits it there) |
 | `v` `V`           | select: the nodes between here and where you started (`V`: with their branches); then `d` `y` `>` `<` `M` or `<Space>c` act on all of them |
 | `M`               | move the branch with `hjkl` (`M` again: just the node) |
+| `<Space>=`        | tidy the branch: `m` a mind map, `c` an org chart, `g` a grid (`:tidy`) |
+| `<Space>a`        | in visual mode: line the selection up, `h` `l` `k` `j` left, right, top, bottom, `c` middles (`:align`; `:` in visual mode runs a command on the selection) |
 | `C`               | connect: go to another node, Enter links them (`d` removes the line, `>` puts it under that node, `<Space>` `a` `l` `c` `s` `t` style it, Esc takes it all back) |
 | `/` `n` `N`       | search: titles, tags and bodies, fuzzily, with the note of each match beside it / the next match / the previous one |
 | `Ctrl-o` `Tab`    | back to where you jumped from / forward again (across documents) |