Don't draw a wait's bar at nothing

A fraction of zero is the absence of a sample, not a measurement of the
work: a bar at nothing for two minutes says the load has not started,
which of one 8 GB into a 12 GB file is false.

Measured raw off the router's event stream today: llama-server reports a
model's load as 0 and then 1 with nothing in between, on both the 0.6B and
the 27B, and reports prompt processing once a batch. So the bar now draws
for a long prompt -- the wait worth watching -- and a load that says
nothing draws none, which is what not knowing should look like.

PLAN.md

@@ -502,6 +502,15 @@ deliberate and easy to undo by accident:
   starts again for each and a bar that only counted up would be lying.
   `/loading [seconds] [stages]` and `/reading [seconds]` in an echo session
   are the rig for the phone's half.
+  **A fraction of zero is not reported at all**, because it is the absence of
+  a sample rather than a measurement: a bar sitting at nothing for two
+  minutes says "this has not started", which of a load 8 GB into a 12 GB file
+  is false. That is not theoretical -- measured 2026-09-21, raw off
+  `/models/sse`, `llama-server` reports a load as **0 and then 1** with
+  nothing in between (both the 0.6B and the 27B), and prompt processing
+  reports **once a batch**, so a prompt under `n_batch` is one step as well.
+  So what usually draws a moving bar is a long prompt, which is also the wait
+  worth watching -- tens of seconds at the context sizes measured above.
 - **Which tools a session offers is a filter here, not a flag there**
   (2026-09-19). The router is always started with `--tools all` and hosts one
   set of tools for the machine — one per session is not a thing a shared