dashboard: messages follow the line they went over

Dots and flashes ran straight from sender to receiver, whatever line
the message took: a PING over another transport, drawn as a curved
line beside the one in use, crossed the map off its line.

Each message now runs along the line it went over, as drawn (`route`:
the link's quadratic curve, its control point where renderGraph put
it): a message naming the address it went to (the paths layer's PINGs
and PONGs) over that address's transport's line, any other over the
line in use; a flash's streak bends with it.

1 files changed, 4 insertions, 1 deletions

diff --git a/docs/dashboard.md b/docs/dashboard.md
index de5fe3e..be57603 100644
--- a/docs/dashboard.md
+++ b/docs/dashboard.md
@@ -136,7 +136,10 @@ drawn hollow) is drawn as the other end reports it, which its tooltip says. Then
   is down (no path to the peer answers; `/peers` shows its connection as `null`).
 
 Messages this node exchanges run along its links as dots, from sender to receiver, all
-at one speed: over a longer link they arrive later.
+at one speed: over a longer link they arrive later. Each follows the line it went over:
+a subscribed node's PING or PONG of the paths layer, which names the address it went
+to, the line of that address's transport (curved, beside the one in use); any other
+(this node's own come as counts, without addresses), the line in use.
 They come from the per-peer message counts, which arrive every 2 s: what was sent and
 received since is spread over the next 2 s, at most 6 dots per link and direction,
 shared out by message kind, each kind in its colour (named in the legend; the console