fix: a source that has sent no CONFIG reads connecting, not connected

A stream that answered CONNECT but has sent no CONFIG has no signal list, so
nothing can be enabled and no DATA frame is owed. Calling that "connected, but
no data is arriving: another reader may hold the source" blamed a second reader
that does not exist, and the badge blinked green over it -- a working pipeline
is exactly what it did not have.

The glance word is `connecting` (ten characters, no wider than `event held`,
so the fixed-set layout rule still holds) and the badge takes a fourth, steady
yellow phase, both from the first frame rather than after the three-second
stall test. The stall notice itself now splits on `have_config`: the unicast
contention wording where a signal list exists, "trying to connect" where it
does not, with `[udpscope] connecting:` on stderr beside the old `starved:`.

src/help/14-status.txt

@@ -9,11 +9,17 @@ The bar is always visible under the plot. Click <b>ⓘ</b> for the detail popove
 
 <b>Worth knowing</b>
 
-• The badge is one glyph in three colours: lit and dim alternating means data is arriving, and a
-  steady idle colour means it is not. A badge that never blinks is not a working badge.
-• The state field is one word from a fixed set: <tt>live</tt>, <tt>paused</tt>, <tt>armed</tt>,
-  <tt>capturing</tt>, <tt>event held</tt>, <tt>disarmed</tt>. Two states add one field each: in
-  trigger mode, how long ago the last event was; while paused, how long you have been paused.
+• The badge is one glyph in four colours: green <i>alternating</i> lit and dim means data is
+  arriving, and a steady colour means it is not. A badge that never blinks is not a working badge.
+  Of the two steady colours, <i>grey</i> is no stream at all or a pipeline you stopped (the
+  tooltip says which), and <i>yellow</i> is a source that answered but has sent no configuration.
+• The state field is one word from a fixed set: <tt>connecting</tt>, <tt>live</tt>,
+  <tt>paused</tt>, <tt>armed</tt>, <tt>capturing</tt>, <tt>event held</tt>, <tt>disarmed</tt>. Two
+  states add one field each: in trigger mode, how long ago the last event was; while paused, how
+  long you have been paused.
+• <tt>connecting</tt> means there is no <i>signal list</i> yet — either no session or a session
+  with no configuration behind it. Every other word claims a signal list, so until one arrives
+  there is nothing for them to describe: nothing can be enabled and no data is owed.
 • The paused figure is <i>wall</i> time, not stream time — the producer never stops while paused,
   so it answers "how long have I been looking at this picture".
 • Nothing on the bar may change width with the stream, because the bar sits directly above the
@@ -24,9 +30,11 @@ The bar is always visible under the plot. Click <b>ⓘ</b> for the detail popove
   non-zero count means samples are absent from the buffer, not merely late.
 • <tt>reconnects</tt> counts sessions re-established with the source. Over unicast a climbing
   count usually means a second client is taking the source's single session.
-• The starvation notice — <i>connected, but no new frames in the last second</i> — is that same
-  situation seen from the other side. Pointing the app at a port where nothing answers produces
-  it too.
+• The starvation notice — <i>connected, but no data is arriving</i> — is that same situation seen
+  from the other side: the signal list is here, so something took the stream away. A source that
+  has sent <i>no</i> configuration gets a different notice, <i>trying to connect</i>, because
+  nothing was taken away — pointing the app at a port where nothing answers is that case, and the
+  usual cause is a streamer that is not running or is serving another port.
 • <tt>stored</tt> versus <tt>wire</tt> in the popover is the decimation. They differ exactly
   when the window is too long to store at full rate.