DO NOT MERGE - scratch probe proving the two lint behaviours from #156

[balbasty]

Throwaway. Not for review, not for merge — will be closed and the branch
deleted as soon as it has produced its evidence.

Exists only to exercise #156's two new lint behaviours against real GitHub
Actions, since #89 happened precisely because nobody ever ran the failure
branch. Based on #156's branch (not main) and adds exactly one file, at a
path matching no entry in the changes filter — so only the lint jobs run:
no test-cpu, no build-cuda.

tests/format_probe.cpp carries two deliberate defects at once:

defect	expected job outcome
#include "fastfields/core/defines.h" — quoted public include	lint (source conventions)RED, naming normalise-include-delimiters and the file:line
deliberate mis-formatting	lint (clang-format, changed lines)GREEN, having printed the diff, a ::notice:: and a step-summary block

The second is the interesting one: green while reporting findings is the whole
point of #156, and the exact case that used to be red-and-silent.

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Generated by Claude Code

[balbasty]

Evidence collected — both behaviours confirmed against real Actions. Closing; branch deleted. Recorded on #156.

Run 32417649104:

job	conclusion
lint (source conventions)	failure	tests/format_probe.cpp:7: fastfields/core/defines.h -- public header, must use <>, exit 1
lint (clang-format, changed lines)	success	printed the full diff and a ##[notice] annotation, exit 0
all test-cpu / build-cuda / test-hub legs	skipped	path matched no filter, as intended

Three things worth recording beyond the headline:

• The clang-format job was green while reporting. That is the exact case that used to be red-and-silent under CI: the clang-format job can never print its findings (set -e kills it before the report) #89.
• The if: !cancelled() guard works: after normalise-include-delimiters failed, normalise-header-guards and rename-macros both still ran and reported clean. A change tripping two conventions hears about both in one run.
• lint (source conventions) finished in ~3 seconds wall clock (21:06:14 → 21:06:17) with no apt and no setup-python, using the runner image's own interpreter.

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Generated by Claude Code