chore: hold the coverage gate at 100%

[tschm]

Coverage is already 100%, so this raises the gate to match it. No tests were added,
because there is nothing uncovered to add them for.

Name                             Stmts   Miss Branch BrPart  Cover
src/cvx/quadprog/__init__.py         5      0      0      0   100%
src/cvx/quadprog/_base.py           26      0      2      0   100%
src/cvx/quadprog/_pdas.py          108      0     28      0   100%
src/cvx/quadprog/_qr.py             57      0     12      0   100%
src/cvx/quadprog/_setup.py          34      0     18      0   100%
src/cvx/quadprog/_solve.py         106      0     26      0   100%
src/cvx/quadprog/_steps.py          52      0     16      0   100%
src/cvx/quadprog/_structure.py      28      0      8      0   100%
src/cvx/quadprog/_sweep.py          87      0     18      0   100%
src/cvx/quadprog/_threads.py       104      0     38      0   100%
TOTAL                              607      0    166      0   100%
1131 passed

The change

python.mk defaults COVERAGE_FAIL_UNDER to 90. That is the right floor for a repo
climbing towards coverage; here it permitted ten points of silent regression. The root
Makefile — repo-owned, and already where MKDOCS_EXTRA_PACKAGES,
LICENSE_IGNORE_PACKAGES and the mutation override live — now sets it to 100.

Placed before include .rhiza/rhiza.mk, so python.mk's ?= sees it already defined,
and written as = rather than ?= for the reason the LICENSE_IGNORE_PACKAGES block
directly below documents: a ?= against a variable the template already defines is a
silent no-op.

Verified — pytest-cov's summary line changes from Required test coverage of 90% reached
to Required test coverage of 100% reached, which is what proves the override actually
reaches the flag.

No workflow passes COVERAGE_FAIL_UNDER on the command line, so nothing overrides this
in CI.

Also corrected

A comment in pyproject.toml claimed the gate was "90%", set by pytest.ini, over "all
three modules". All three parts were wrong: it is set via COVERAGE_FAIL_UNDER (not
pytest.ini), it is now 100, and the package has been ten modules for a while.

What this does and does not buy

It is a ratchet against untested code arriving — nothing more. Line-and-branch coverage
says every line ran, not that any assertion would have noticed if it misbehaved. make mutation is the gate that asks the second question, and it remains the more informative
one for a numerical package.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR tightens the project’s test coverage enforcement by raising the coverage fail-under threshold to match the repo’s current 100% coverage, and updates related documentation comments to reflect how the gate is configured.

Changes:

• Set COVERAGE_FAIL_UNDER = 100 in the root Makefile so the Rhiza python.mk coverage gate enforces 100%.
• Updated pyproject.toml commentary to reflect the gate source (COVERAGE_FAIL_UNDER) and the current module count.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
Makefile	Overrides template default coverage threshold to enforce 100% coverage.
pyproject.toml	Updates explanatory comments about how coverage/test-layout expectations are enforced.

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