ci: switch firmware formatting to clang-format and add test-vector validation

[tmarhguy]

Motivation

• Ensure ALU test vectors are syntactically and structurally valid before merging by adding a JSON Schema and validator.
• Replace the Arduino CLI formatting check with clang-format to provide a reproducible, installable formatter for .ino files.
• Provide a documented local workflow so developers can run the same checks CI will run.
• Clean up Arduino sketches so they pass the repository formatting rules.

Description

• Updated the CI workflow .github/workflows/ci.yml to install jsonschema and clang-format==18.1.5, run tools/validate_test_vectors.py, and run clang-format --dry-run --Werror --style=file against all *.ino files.
• Added a repository .clang-format style file to define formatting rules and updated README.md with local validation commands using pinned tool versions.
• Added test/schema/test-vector.schema.json and tools/validate_test_vectors.py, plus a test/vectors/.gitkeep placeholder, to validate JSON test vectors.
• Cleaned whitespace/formatting in Arduino sketches miscellaneous/firmware/controller-display/controller_display.ino and miscellaneous/firmware/controller-input/controller_input.ino to satisfy the formatter.

Testing

• No automated tests were executed as part of this rollout.
• The repository's CI verify job had previously failed on the branch before these formatting changes, and CI has not been re-run since switching to clang-format.
• The tools/validate_test_vectors.py script is included and will return non-zero on validation or JSON parse errors, causing CI to fail when invalid vectors are present.
• Local validation commands are documented in README.md so developers can run the same checks prior to opening a PR.

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Codex Task