Add the board, and finish v1.1 (stage 9e)

The board is the user's design: the document as lists and blocks, the
way Scratch nests blocks inside a loop. Each node without a parent (the
root, then each loose node) is a column with its title in the top border;
its children are cards in it, one under the other; a card with children
on show wraps them in a C: a joint at its bottom left, a bracket down the
left two cells further in, and a foot closing it. Blocks nest as deep as
the tree does. The columns by tag or color the first design had are
dropped (the user's pick), and :board takes no arguments any more.

j and k go down and up a column in reading order, into the blocks; h and
l go to the column beside, onto the card nearest the cursor's height.
Titles are typed right in their cards, and visual mode selects in
reading order as the outline does. <Space>vb or :board shows it.

Move mode (M, the user's pick) moves the card through the tree: h and l
to the end of the column beside, j and k past the cards around it, into
an open block and out of one at its end. A column's own node trades
places with the loose column beside it; the root's column stays first.
A drag does the same with the mouse: dropped on a card it goes after it,
on a block's card into it, on a column at its end.

The fallback message for a key a view ignores now names the view ("does
nothing in the board view"). The version goes to 1.1.0: stage 9 is done.

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

DESIGN.md

@@ -334,6 +334,31 @@ lines.
   list: the matches as they were when you searched. `/` and `:find` still
   search the document shown, and `n` after them stays in it.
 
+**The board** (settled in part 9e, the user's design)
+- The board shows the document as lists and blocks, the way Scratch nests
+  blocks inside a loop: each node without a parent (the root, and each
+  loose node) is a column, with its title in the column's top border; its
+  children are cards in it, one under the other; and a card with children
+  on show wraps them in a "C": a `├` at its bottom left, a bracket down the
+  left past its cards (two cells further in), and a foot closing it. Blocks
+  nest as deep as the tree does. The columns by tag or by color the first
+  design had are dropped (the user's pick).
+- A card is a node's box, as on the canvas: its title, its tags and badge
+  in the bottom border, its color on the border, thick for the cursor.
+  Folds fold here too (a folded block is a card with `+N`).
+- `j` and `k` go down and up a column in reading order (into the blocks),
+  `h` and `l` to the column beside, onto the card nearest the cursor's
+  height. Titles are typed right in their cards, and `<Space>vb` or
+  `:board` shows it.
+- Move mode (`M`, the user's pick) moves the card instead: `h` and `l` to
+  the end of the column beside, `j` and `k` past the cards around it, into
+  a block (as its first card going down, its last going up) and out of one
+  at its end; a column's own node trades places with the column beside
+  (the root's stays first). Enter is done, one undo step. A drag does the
+  same with the mouse: dropped on a card, it goes after it; on a block's
+  card, into it; on a column, at its end. Every move goes through the tree.
+- In visual mode the board selects in reading order, as the outline does.
+
 **Views, panes and popups** (settled in stage 7)
 - The Note view is made of parts: the title, the tags, the body, each link
   (out, then in) and each child. `j` and `k` step through them, with a bar
@@ -514,7 +539,7 @@ backlinks, and the backlink paths in every document it points to.
 | **Canvas** | The 2D map: free placement, 3 zoom levels, right-angle lines and the mouse. |
 | **Outline** | Reorganizing and reading: an indented tree with fold markers, `+N` for hidden nodes and `»` for portals, with loose nodes listed at the end. |
 | **Note** | Writing: one node's title, tags, color and body (with vim motions inside), plus its links in and out and its children. It follows the cursor. |
-| **Board** (v1.1) | Sorting: columns by tag or color. Moving a card to another column changes its tag. |
+| **Board** (v1.1) | Lists and blocks: a column per node without a parent, its children as cards, and a card with children wrapping them, as Scratch's loop blocks do. |
 
 - **Pickers:** documents, colors, borders, styles and tags in v1; Search in v1.1.
 - **Popups:** which-key (bottom right, as in skyshift), `?` help, the `K` card,
@@ -531,7 +556,8 @@ pans up and down, and sideways with a wheel that tilts, a touchpad, or the
 wheel with Shift or Alt held (Alt for terminals that keep Shift for selecting
 text), Ctrl+drag selects a rectangle, Ctrl+click adds or removes one node,
 right-click opens a menu built from the same actions as the keys. Zoom is on
-the `+` and `-` keys.
+the `+` and `-` keys. On the board, dragging a card moves it in the tree:
+after the card it's dropped on, into a block, or to the end of a column.
 
 ## Modes and keys
 
@@ -563,10 +589,11 @@ text).
 | **Create and edit** | `o` `O` sibling below / above · `a` child · `i` `A` Enter edit the title · `I` edit from its start · `cc` `S` retype |
 | **Operators** | `dd` or `dab` delete branch · `dib` delete children · `x` delete just the node · `yy` `yab` `yib` yank · `p` paste as children · `P` paste as siblings below · `>>` `<<` indent / outdent · `"a`–`"z` and `"+` registers · `.` repeat · `u` `Ctrl-r` undo / redo |
 | **Modes** | `v` `V` visual · `M` move · `C` connect · `:` command · Esc back to normal |
-| **Leader** `<Space>` | `c` color · `s` style · `B` border · `t` tags · `=` tidy (`m` map, `c` chart, `g` grid) · `p` new portal (`:portal `) · `o` this branch out, to a document of its own · `/` search every document · `i` inbox · `b` documents · `v` then `c`/`o`/`n` for canvas / outline / note · `w` which-key on/off · `?` help |
+| **Leader** `<Space>` | `c` color · `s` style · `B` border · `t` tags · `=` tidy (`m` map, `c` chart, `g` grid) · `p` new portal (`:portal `) · `o` this branch out, to a document of its own · `/` search every document · `i` inbox · `b` documents · `v` then `c`/`o`/`n`/`b` for canvas / outline / note / board · `w` which-key on/off · `?` help |
 | **Panes, documents** | `Ctrl-w v` `Ctrl-w s` split · `Ctrl-w hjkl` focus · `Ctrl-w w` the next pane · `Ctrl-w c` close · `Ctrl-w o` only · `Ctrl-w =` even sizes · `gt` `gT` `]b` `[b` next / previous document · `ZZ` close pane (the last one quits) |
 | **Outline** | `j` `k` rows · `h` `l` parent / first child · `zb` every body · `M` then `j` `k` (`J` `K`: 5) swap with siblings, `h` out, `l` under the one above |
 | **Note view** | `j` `k` parts · Enter `i` `A` edit the part (`I` from its start, `cc` `S` anew), or go to that link or child · `h` `l` the sibling before / after |
+| **Board** | `j` `k` cards in a column · `h` `l` the column beside · `M` then `h` `l` to the column beside, `j` `k` down and up (into and out of blocks) · drag a card |
 | **Lists** (help, menu, pickers) | `j` `k` `gg` `G` `Ctrl-d` `Ctrl-u` move · `/` search · Enter pick or run · Esc or `q` close |
 | **K card** | `j` `k` `Ctrl-d` `Ctrl-u` scroll · `i` `A` Enter edit the body (`I` from its start) · `K` `q` Esc close |
 | **Typing** | `Backspace` `Delete` · `Ctrl-w` delete word · `Ctrl-u` delete line · arrows, Home, End · Enter (title: done, or after `o O a` the next idea; body: new line) · Tab Shift-Tab (a new idea: under the one above / out a level) · Esc to vim keys |
@@ -747,7 +774,7 @@ cumulus/
    │               keymap (+ keys.toml), engine (counts, registers, operators), mouse
    ├─ command/     registry, parse, complete, history
    ├─ view/        mod.rs (the View trait), canvas/ (camera, boxes, lines, route, scene, render,
-   │               navigate, placement, arrange (:tidy, :align), view), outline, note; later board
+   │               navigate, placement, arrange (:tidy, :align), view), outline, note, board
    ├─ ui/          text_input (a line of text and its cursor), text_editor/ (vim inside text:
    │               motion, object, layout), list (the popup list help, menus and pickers
    │               share), card (the K card), status_bar, document_bar, which_key,
@@ -776,7 +803,7 @@ cumulus/
 The end-to-end tests are in `app/tests.rs` (with `app/tests/files.rs`,
 `app/tests/config.rs`, `app/tests/vim.rs`, `app/tests/connect.rs`,
 `app/tests/portals.rs`, `app/tests/arrange.rs`, `app/tests/branch_out.rs`,
-`app/tests/export.rs` and `app/tests/everywhere.rs`):
+`app/tests/export.rs`, `app/tests/everywhere.rs` and `app/tests/board.rs`):
 they copy the sample
 documents to a temporary folder, type keys and click on a test terminal, and
 check the screen, the documents and the files.