commands: one grammar for !, merged commands, a settings sheet, two-level help

A `!` now means force or everything and nothing else (`:w!`, `:search!`,
`:export!`, `:logout!`). A command that did a second thing behind its bang
takes a word for it instead: `:space new|name|rm`, `:list name|rm`,
`:task [add]|edit`, `:upload seal`, `:import zip [/]`. `:card` while reading
a document makes a card about it, so `:card!` is gone.

Merged: `:export` downloads what has focus, a file as it is or a document as
markdown (`:download` folded in); `:share [off|new]` replaces `:unshare` and
`:link`, and the list's `s` and `y` give way to it and the info sheet;
`:noh` replaces `:clear`; `:vault [unlock|lock|passwd]` replaces `:unlock`,
`:lock` and `:passwd`; Esc in the list puts down what `m` picked up before it
closes the document, replacing `:unmark`.

The old spellings run as their new lines for one release through a table in
commands.ts; help and Tab leave them out, and the wiki lists them.

A settings sheet (`,` or `:settings`) holds the options, the vault, the
backup, the signed-in browsers, ssh keys and capture tokens. Each row runs
the command a line would. Bare `:set`, `:vault`, `:backup`, `:sessions`,
`:sshkey` and `:token` open it at their part.

`?` shows the keys and commands to start with, flagged in the keymap and the
command table; a second `?` (or `:help all`) shows all of them, and a filter
always searches all of them. Help rows are keyed by key and description, as
two contexts can share a label.

docs/wiki/Vault.md

@@ -14,12 +14,12 @@ the vault is shut.
 
 | command | what it does |
 | --- | --- |
-| `:vault` | set the password the first time (ten characters at least); afterwards, say whether the vault is open |
-| `:unlock` / `:lock` | open / close the vault |
-| `:upload!` | upload files sealed, encrypted as they stream in, so the plaintext never touches the disk |
+| `:vault` | set the password the first time (ten characters at least); afterwards, the vault in the settings sheet (`,`), where `Enter` opens or locks it |
+| `:vault unlock` / `:vault lock` | open / close the vault |
+| `:upload seal` | upload files sealed, encrypted as they stream in, so the plaintext never touches the disk |
 | `:encrypt` | seal the file under the cursor; on a folder or space, seal it for good |
 | `:decrypt` | take the file, or the sealed folder, back out |
-| `:passwd` | change the password |
+| `:vault passwd` | change the password |
 
 A sealed file carries a lock in the list, and the bar says `vault open` while it
 is. While the vault is shut, `Enter` on a sealed file asks for the password.
@@ -51,7 +51,7 @@ copy once the vault shuts. A sealed file is never indexed for search.
 
 ## Changing the password
 
-`:passwd` makes a new master key as well as a new password. The old password
+`:vault passwd` makes a new master key as well as a new password. The old password
 stops opening anything at once. Every sealed file is then sealed again under the
 new key in the background while the vault is open; `:vault` shows how far it
 has come. After that, an old copy of `diary.db` together with the old password