Enforced a coverage floor on the merged report (#667)

The coverage summary reported a percentage and could not fail. Coverage
could fall from 99.97% to anything at all and every check stayed green,
against an AGENTS.md that asks for 100% test coverage -- a stated
requirement measured with a gauge that had no failure mode.

CodeCoverageSummary already takes thresholds and fail_below_min; neither
was set. Both are now, through a new coverage_thresholds input on the
template, because the two suites do not sit at the same figure: ThreadX
99, SMP 98.

Three things were probed against the pinned action on a runner before
picking those numbers, using the real merged.xml files from the dev push
run of #666.

The floor compares the line rate and nothing else. That mattered because
branch coverage is around 78% in both suites while line coverage is
98.8-100%, so a floor aimed at the line figure would have been an
immediate red wall had it tested branches or the lower of the two. The
ThreadX report at 100.00% lines and 77.67% branches clears a floor of 99.

The thresholds are whole numbers. '99.9 100' -- the value this was meant
to be -- is rejected with 'System.ArgumentException - Threshold parameter
set incorrectly.', and the step fails whether or not fail_below_min is
set. So the choice is 99 or 100 with nothing between.

100 would fail on a race. tx_thread_system_resume.c:529 is reached by
timing rather than by construction and flaps between runs of the same
green tree, which is why #666 left it; 4502/4503 fails a floor of 100 and
clears one of 99. A coverage gate that goes red on a coin toss is how
coverage gates get switched off.

SMP is 5114/5178 lines, 98.76%, with 64 uncovered lines across 11 files
of common_smp/src -- #666 closed the equivalent gaps in common/src only.
A shared floor of 99 would have failed that job on every run while
ThreadX passed.

One limit is recorded in the file rather than fixed: an empty report
reads as 100%. gcovr writes line-rate="1.0" beside lines-valid="0" when
it finds no data, and the action prints 'Line Rate = 100% (0 / 0)' and
passes any floor. The check for that is the emptiness assertion #664 put
in each suite's coverage.sh, not this one.

Also corrected two stale filenames in the deploy job's comment: since
#665 each coverage artifact carries merged.xml, not
default_build_coverage.xml. Verified on the runner.

Assisted-by: Claude Opus 5 <[email protected]>

0 files changed, 0 insertions, 0 deletions