deps: the libavr pin advances, and the tiny85 image grows 24 B

The growth is not this bump's. It entered at libavr 32f8167, where the
software master started clocking the rate it is told: the phase padding has to
cover the shortest bit of a byte, and paying for it costs `shift_out` and
`read_acked` twelve bytes each on the tiny85. Those two symbols are the whole
of the move - an avr-nm diff across the two images names them and nothing else.

So the claim went unheld through two pin bumps. 1246 B was last measured at
libavr e697920; the tiny85 preset has read 1270 since 32f8167, which both
5a042a9 and f2205a7 pinned past without re-recording it. The number is stated
in test/CMakeLists.txt and in README.md, and this is what keeps them one fact -
a check that only ever ran on one of the two chips keeps neither.

The suite also stops depending on its host: libavr's launcher and skip marker
register every check everywhere, and one this machine cannot run reads as
Skipped rather than going missing.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

README.md

@@ -27,7 +27,7 @@ cmake --build --preset attiny85-generated
 Presets cover attiny85/atmega328p in both libavr modes (generated and
 reflect); `ctest` runs the consteval battery over the BCD, the hours
 register's two formats, the weekday and the alarm rate encodings, and holds
-the example to its stated size — **1480 B** on the mega328P and **1246 B**
+the example to its stated size — **1480 B** on the mega328P and **1270 B**
 on the tiny85, byte-identical across the two modes. The legacy
 yazoalfa-based driver lives on the `master` branch.