docs/re: flag the load confound behind the input and boot-time numbers

The container runs the emulator, the Canary build and the disc test suite on the
same 12 cores, and Xenia alone takes about 5.5 of them. Several (A) experiments
and most boot-duration numbers in this entry were measured while a cargo test or
a build was running; one boot under that load never reached the title in 400 s,
against 130-290 s unloaded.

It does not explain the (A) result by itself — the interleaved A/B alternated
arms under whatever load was present, and the latest title recorded accepted
while an earlier one refused — but "a starved guest misses the input window" is a
hypothesis the existing data cannot exclude, and it should have been flagged when
the numbers were taken rather than after. The same navigation is now being run on
an idle box.

docs/re/canary-scripted-input-traps.md

@@ -299,3 +299,19 @@ changes. Whatever ignores Ⓐ at an attract title is a *consumer* further up, an
 finding it means identifying the object the poller fills (passed in as `r3` from
 the per-frame update) and then its readers. That is a real RE job, not a
 one-iteration probe, and it is where this thread now stands.
+
+### A confound in all of the above: the box was not always idle
+
+Worth recording against every timing number in this entry. The container runs
+the emulator, the Canary build, and Reborn's disc test suite on the same 12
+cores, and Xenia alone uses about **5.5**. Several of the Ⓐ experiments — and
+most of the boot-duration measurements — were taken while a `cargo test` or a
+`build-canary` was running. One boot then failed to reach the title at all
+within 400 s, where an unloaded boot reaches it in 130–290 s.
+
+That does not explain the Ⓐ result on its own: the interleaved A/B alternated
+arms under whatever load was present, and the latest title of all (268 s)
+*accepted* while a 232 s title refused. But a starved guest missing an input
+window is a live hypothesis that the data collected so far cannot exclude, and
+the honest next measurement is the one now being taken — the same navigation on
+an **idle** box, with nothing else running.