re: rest() fixed -- a trailing keyframe run is the hold when it is

VISIBLE, not when its pose repeats

The port agent's report was right about the defect and about which
elements it hits, and its proposed condition does not survive the case
the exclusion was written for.

Their test -- the final untimed keyframe has the same pose as the last
timed one -- is also true of pgptitle.rat, whose trailing run is two
identical transparent frames. Adopting it would erase the word PAUSE
again, which a committed capture disproves. What separates the two is
alpha: an exit fades the element out so its last keyframe is transparent,
while an element with no exit ends on the pose you can see. So
rest_plateau now accepts a trailing run exactly when it is visible.

Verified against a capture rather than against another renderer, which is
the point their own report made: ptframe1's rest moves from (620,108)
t=16 to (440,108) t=62; the changed pixels are 10082 in a bounding box of
x 440-839, y 108-577, which is exactly the 400x470 at (440,108) they
predicted; and correlation against main-menu-oracle.png over that region
improves from 0.9596 to 0.9748. The PAUSE wordmark is unchanged across
all three pause builds.

This also closes a question ui-paint-order-key.md has carried for a
while, that ptframe1 and ptframe2 rest at alpha 0 while the capture shows
the menu frame plainly.

One trap cost most of this iteration and goes in METHOD: CARGO_TARGET_DIR
is redirected in this container, so ./target/debug/sylpheed-cli is hours
stale and every render I made against it was old code. Byte-identical
before and after reads as "no effect" when it actually means "you ran the
old binary".

The full disc-gated test suite was still executing when this was
committed; the verification above is artifact-based.

docs/re/METHOD.md

@@ -268,3 +268,10 @@ agent's loop prompt, i.e. nowhere durable. See [`README.md`](README.md) for the
   the decode's determinism, not its truth. Only a framebuffer capture is an
   independent check. (Reported by the port agent, 2026-08-28, after a capture
   crop found the missing bracket.)
+* **`./target/debug/<bin>` is STALE in this container — `CARGO_TARGET_DIR` is
+  redirected.** The Dockerfile sets `CARGO_TARGET_DIR=/sylph-home/re/target-container`
+  so a fresh `cargo build` writes there, while `./target/debug/sylpheed-cli`
+  remains whatever was built on the host, hours old. A decoder fix was verified
+  against the stale binary and produced byte-identical "before" and "after"
+  renders — which reads exactly like "the change had no effect" rather than "you
+  ran the old code". Run the binary cargo actually wrote, or `cargo run`.