docs: the two sweep flakes are fixed, and one assertion that could not fail

bus-conformance.md still listed the example_demo root count and
session_over_one_router as not fixed here. Both are fixed on main now, so
the rows say what each test does instead: the example waits for the
producer's hold release before reading the counts, with its printed
output unchanged, and the integration renderer is held until the
publisher's twentieth receipt has returned, so its coalescing is forced
and the assertions are order, freshness, acceptance under a stalled
spectator and the replacement accounting, with the before and after
counts.

The delivery check in that test compared (step, sequence) against
(step, step), whose first element can never fail. It compares sequence
against step.

docs/design/session-framework/bus-conformance.md

@@ -438,18 +438,30 @@ poll-until-the-router-settles the rest of the file already uses for router-side
 no sleep, no timing constant, and the assertion now has the precondition its contract sentence
 names. **360 runs after the fix, 0 failures** (240 debug, 120 release).
 
-Two other intermittent failures were seen in the same sweep and are **not** fixed here, since
-they belong to the bus slice rather than to this one:
+Two other intermittent failures were seen in the same sweep. They belonged to the bus slice
+rather than to this one and were fixed there, in the same way and for the same reason:
 
 - `tests/example_demo.rs::the_example_shows_a_counter_rpc_an_observer_and_a_held_frame`,
-  2 failures in 40 standalone runs plus 1 in 12 full-suite runs. It prints
+  2 failures in 40 standalone runs plus 1 in 12 full-suite runs. It printed
   "while the frame is held: 1 artifact(s), 2 root(s)" instead of 1 root: the producer's hold
   release is queued on the control lane and had not been applied when the example read the
-  counts. The same shape of gap, in the guide deliverable's printed output.
-- `tests/integration.rs::unix_socket::session_over_one_router`, 1 failure in 12 full-suite
-  runs and 0 in 40 standalone runs, at the assertion that the deliberately slow consumer
-  skipped snapshots. Under load it kept up, so the assertion is a timing claim about the
-  machine.
+  counts. `examples/demo.rs` now waits for that release before reading the counts, the same
+  bounded poll it already used for collection eight lines below, so the line the guide quotes
+  is an observation rather than a race. The printed output is unchanged.
+- `tests/integration.rs::session_over_one_router`, 1 failure in 12 full-suite runs and 0 in 40
+  standalone runs, at the assertion that the deliberately slow consumer skipped snapshots.
+  Under load it kept up, so the assertion was a timing claim about the machine: section 7
+  permits a latest subscriber to miss values, it does not oblige it to. The renderer is now
+  held until the publisher's twentieth receipt has returned -- the publisher's completion
+  observed, not timed -- so the coalescing is forced by construction, and the test asserts the
+  guarantees that do hold: each delivery carries the frame of the snapshot it announces,
+  deliveries arrive in publication order, the last value received is the latest published, the
+  renderer receives snapshots 1 and 20 of 20, both subscriptions accept all twenty publications
+  while the spectator reads nothing, and the eighteen replacements reported to the publisher at
+  admission are the same eighteen reported to the renderer on delivery and are exactly the
+  snapshots it did not receive. 16 failures in 40 runs beside four busy loops before, 0 in 40
+  after; the whole crate went from 10 failed runs in 20 to 0, and the workspace suite from 2
+  in 5 to 0.
 
 ## Contradictions
 

services/flysim/crates/flybus/tests/integration.rs

@@ -168,8 +168,7 @@ async fn session_over_one_router(via: Via) {
             let bytes = frame.read_all().await.unwrap();
             let step = bytes[0] as u64;
             assert_eq!(
-                (step, sequence),
-                (step, step),
+                sequence, step,
                 "a delivery carries the frame of the snapshot it announces"
             );
             coalesced += replaced;