* ci: centralize protoc setup in a composite action
Add .github/actions/setup-protoc that pins both the arduino/setup-protoc
SHA and the protoc version (34.1) in one place, so future bumps no longer
require touching every workflow.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
* ci: replace arduino/setup-protoc with direct release-zip download
The arduino action queries the GitHub API on every invocation even when
the version is fully pinned, which is unnecessary work. Inline a small
shell step that downloads the protoc release zip directly using
RUNNER_OS/RUNNER_ARCH for asset selection. Supports Linux, macOS, and
Windows (x64 + arm64 where protobuf publishes assets).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
