Make the docs state things rather than argue them

The site read as a design journal: rationale paragraphs, hedges
("deliberately", "on purpose", "genuinely"), meta-commentary about the docs
themselves, and one em-dash every ten lines carrying an aside.

Roughly twenty rationale blocks are gone or reduced to what a reader needs
in order to use the thing. Em-dashes go from 507 to 135, and what is left is
structural rather than prose: list and definition separators, table cells,
and four inside code blocks that quote what the CLI actually prints.

Also: api.example.com becomes api.fluksio.com (the emails stay, since
bootstrap.py really defaults to admin@example.com and RFC 2606 reserves it);
the mqtt table gains the two settings it had drifted behind on and inject's
wording matches the engine; llms.txt lists the two connector pages that were
in the nav but not in it; and the two device/device_policy notes now agree.

Builds clean under `zensical build --strict`.

docs/interface/index.md

@@ -1,6 +1,6 @@
 # The dashboard app
 
-The web interface is a single-page app served at `app.${DOMAIN}` — or, for an
+The web interface is a single-page app served at `app.${DOMAIN}`, or, for an
 instance reached through a portal, at `${DOMAIN}/i/{instance-id}`.
 Either way it is the same application, and it is a client of the same REST API
 you can script against.
@@ -54,7 +54,7 @@ Each flow also has a switch beside it in the list, which starts and stops it.
 
 Two columns under the graph, exactly as tall as each other, most recently
 worked on first. The flows column is the list with the switches; the dashboards
-column is a mosaic, each tile a schematic of that dashboard's layout — blocks
+column is a mosaic, each tile a schematic of that dashboard's layout: blocks
 where its widgets sit, shaded by what kind of widget each one is. Neither
 column grows past about six rows: past that it scrolls in place rather than
 pushing the health block down the page.
@@ -98,7 +98,7 @@ Opening one takes you to [the flow editor](flow-editor.md).
 
 ### Deleting several at once
 
-Press and hold a card — or ctrl-click it — to pick it, then tap the rest. While
+Press and hold a card, or ctrl-click it, to pick it, then tap the rest. While
 anything is picked, **New flow** in the toolbar becomes a trash button, and it
 asks once before deleting the lot. Unpicking the last one puts the list back;
 so does Escape. The Dashboards screen works the same way.
@@ -117,5 +117,5 @@ so does Escape. The Dashboards screen works the same way.
 ## Appearance
 
 Light and dark follow your system by default; **Settings → Appearance**
-overrides it. Both themes are first-class — the wall-panel view in particular is
-designed to be legible in dark from across a room.
+overrides it. Both themes are first-class, and the wall-panel view is designed
+to be legible in dark from across a room.