build: the libavr pin advances past phase 6

The renames land (interrupt_guard, consume_reset_cause, set_duty), the
sampler binds its input in the new converter shape (the input pack plus
in<>::start() as free-running's one kick), and the console states
.allow_baud_error = true for the 115200-at-16-MHz this board has always
spoken - the receiver-tolerance table libavr now enforces is stricter
than the rate's own +2.1 %. The loader probe reads through
avr::flash_load instead of raw pgmspace, the terminal's line buffer is
std::array with backspace and delete named, the tree is reformatted
under InsertBraces, and the sources are ASCII.

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

.clang-format

@@ -1,13 +1,15 @@
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-AlwaysBreakTemplateDeclarations: true
+BreakTemplateDeclarations: Yes
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+InsertBraces: true
 ...