docs(rss-bridge): the install-test went green, and the chart is ruled out as the cause

This chart's install-test had failed on the Gitea runner since the move
(#51): php-fpm as uid 33 unable to read /app/index.php, the startup probe
403ing through its whole 150s budget, the pod never Ready. The chart was
deliberately kept OUT of ci/excluded-charts.txt so that a pass would be
noticed rather than silenced.

It passed, in this PR. Measured from the run: k3d cluster up, helm install
in Ingress mode, pod 1/1 Ready in 22s with 0 restarts, no "Permission
denied" anywhere in the job, and all eight check contexts green.

The chart is ruled out as the cause by a diff rather than by an argument:
the rendered output for the fixture values is BYTE-IDENTICAL to
origin/main - proven in the previous commit to justify the Minor bump - so
the pod spec that succeeded is, line for line, the pod spec that had been
failing. The implicated layer is the runner, which is where #51 had
already placed the burden of proof. The control case arrived for free,
from evidence collected for an unrelated reason.

What this does NOT establish, and the docs say so: that it is repaired.
It is one run, nobody has identified what changed on the runner, and an
intermittent effect needs several runs per side. #51 therefore stays open
and is to be closed on a cause, not on a colour - which was the standing
instruction there before the green arrived.

Corrected accordingly, because shipping documentation that says the test
fails while it demonstrably passed is the half-finished state this repo
tries not to leave behind:

  - README: the httproute-test paragraph, guideline 4's closing passage on
    the last chart of the sweep, and the chart table row.
  - rss-bridge/templates/NOTES.txt: the Gateway branch no longer claims
    the chart has no successful install-test. What remains true, and is
    what it now says, is that the install-test installs the INGRESS mode,
    so the Gateway mode is render-only - the same position as all 21 other
    charts of the sweep rather than a worse one.
  - ci/httproute/rss-bridge.yaml: same correction, plus why the overlay
    stays load-bearing either way.

The wiki carries the same correction in the same round (rss-bridge, CI-CD)
plus a Lessons-Learned entry on the decision that produced the signal: an
excluded test is not a quiet test but a blind one, because you also lose
the moment the fault stops existing.

rss-bridge/templates/NOTES.txt

@@ -70,10 +70,10 @@ Two things do become inert, and neither is a loss:
     intricate Ingress-mode machinery and it simply has no job here.
 
 What is NOT demonstrated: that traffic actually flows. No Gateway controller
-runs in this chart's CI, so no HTTPRoute of it has ever reached
-"Accepted: True" there, and this chart has no successful install-test at all
-(Gitea #51 - a runner defect, unrelated to this mode). Check the route status
-above after the first install rather than assuming it attached.
+runs in CI, so no HTTPRoute of this chart has ever reached "Accepted: True"
+there, and the install-test installs the Ingress mode rather than this one.
+Check the route status above after the first install rather than assuming it
+attached.
 {{- else -}}
 ACCESS - NEITHER INGRESS NOR HTTPROUTE