docs: the guide around four things and two screens, new screenshots, the plan closed

The guide opens with documents, cards, notes and diary entries, and the
documents and plan screens, then walks the day with the scratchpad, the
info sheet and cards linked both ways. The README and the wiki's home say
the same in short, and show the scratchpad and the info sheet. The
screenshot script drops its Alt keys and takes both. PLAN.md records the
simplification's slices, what was left of its navigation fixes, and the
backlog fitted to the model.

docs/wiki/Home.md

@@ -7,6 +7,11 @@ notes for work and for uni, a board per space, and the files that go with them.
 One user, one SQLite file, one binary. Everything is a key or a `:` command on
 the desktop, and a button on the phone.
 
+It keeps four things: **documents**, the thorough record; **cards**, the short
+summary of work, usually about a document; **notes**, jotted in passing on the
+scratchpad until they become one of the others; and **diary entries**. The
+[guide](Guide.md#four-things-two-screens) says how they fit together.
+
 ![A document open in the reader](../images/document.png)
 
 ## Where to start
@@ -22,8 +27,8 @@ the desktop, and a button on the phone.
 | page | what it covers |
 | --- | --- |
 | [Spaces and documents](Spaces-and-Documents.md) | spaces, folders, the list, tiles, moving things |
-| [Writing](Writing.md) | the editor, vim, markdown, math, links between documents, templates |
-| [Boards and the agenda](Boards-and-Agenda.md) | cards, due dates, cards that come back, the agenda |
+| [Writing](Writing.md) | the editor, vim, the scratchpad, markdown, math, links between documents, templates |
+| [Boards and the agenda](Boards-and-Agenda.md) | cards, due dates, cards that come back, the plan screen, the agenda |
 | [The diary](Diary.md) | entries, today, the calendar, on this day |
 | [Files and search](Files-and-Search.md) | uploads, what opens in place, full-text search |
 | [Not losing things](Not-Losing-Things.md) | autosave, history, the trash, export and import |
@@ -47,3 +52,5 @@ the desktop, and a button on the phone.
 | The agenda: what is late, due, or in hand, on every board. | The diary by month. |
 | ![Search reaching into a log file](../images/search.png) | ![A certificate read in place](../images/file-certificate.png) |
 | A search finds the text inside files too. | Certificates and keys are read on the server. |
+| ![The scratchpad](../images/scratch.png) | ![A document's info sheet](../images/info.png) |
+| The scratchpad, lowered over the documents. | The cards about a document, in its info sheet. |