Draw charts from one categorical palette, --chart-1…8

The one-hue ramp told lines apart by lightness alone. --chart-1 is now
--primary and slots 2-8 are distinct hues (orange, violet, green, orchid,
ochre, teal, magenta) that clear 3:1 on --card and stay apart under
protanopia and deuteranopia; red and sage are left out as the status
colours. A chart takes the slots in order instead of spreading a ramp,
and a dashboard's own palette continues after its primary and listed
colours with slots 2-8 rather than tints of its scheme. Line charts stay
at five series. Tokens mirror index's, as design-check requires.

docs/interface/dashboards.md

@@ -71,9 +71,9 @@ takes a `bool`, a gauge takes a number, an agenda takes a `list`, a
 notification takes a `record`. Bind one wrong and the editor says so rather
 than drawing nothing. The same table is enforced on the server.
 
-Charts are the exception worth knowing: because identity across five series is
-carried by lightness alone, a chart with more than one series always draws a
-legend.
+Charts draw their series in one fixed order of colours: the primary first, then
+hues picked to stay apart, colour blindness included. A chart with more than
+one series still always draws a legend, so no line is told by colour alone.
 
 ## Two kinds of chart
 
@@ -200,9 +200,9 @@ A palette is an ordered list of colours, and **position is the role**:
 | 1 | the ground the dashboard sits on |
 | 2 | the surface a widget is |
 | 3 | the primary — fills, active controls, the first chart line |
-| 4 | the accent — the second chart line |
+| 4 | the accent |
 | 5 | text |
-| 6+ | further chart colours |
+| 6+ | the next chart lines, before the app's own chart colours |
 
 Paste a [coolors.co](https://coolors.co) link (or a list of hex colours) and the
 whole dashboard is recoloured: every widget, the rail and the charts. Leave the