fixup: lower coverage floor 92→86 to match post-omit measurement

The 97% number from CI run 24956647701 was measured WITHOUT a
.coveragerc omit list. Once this PR's prescribed omit set is in
effect (`*/__init__.py`, `*/tests/*`, `plugins_registry/*` — files
that don't carry behavior), the actual measurement of behavior-bearing
code on the same staging snapshot is 91.11% (run 24957664272).

86% sits at the issue's prescribed `current − 5pp` margin and
unblocks CI without lowering the bar in real terms.

workspace/pytest.ini

@@ -5,15 +5,22 @@ python_functions = test_*
 asyncio_mode = auto
 # Coverage config moved here from .github/workflows/ci.yml so local
 # `pytest` matches CI without operator-typed flags. cov-fail-under
-# pins the floor at 92% — 5pp below the 97% measured on staging
-# (run 24956647701, 2026-04-26). Floor exists so a regression that
-# drops coverage doesn't sneak past CI; tightening above 92% should
+# pins the floor at 86% — 5pp below the 91.11% measured on staging
+# (run 24957664272, 2026-04-26). Floor exists so a regression that
+# drops coverage doesn't sneak past CI; tightening above 86% should
 # follow real measurement, not aspiration. See issue #1817.
+#
+# Why 86 not 92: the earlier 97% measurement was without the
+# .coveragerc omit list. Once `*/__init__.py`, `*/tests/*`, and
+# `plugins_registry/*` are excluded (the issue's prescribed omit
+# set, more meaningful since those files don't carry behavior),
+# the actual measurement of behavior-bearing code is 91.11% — and
+# 86% sits at the issue's prescribed `current - 5pp` margin.
 addopts =
     -q
     --cov=.
     --cov-report=term-missing
-    --cov-fail-under=92
+    --cov-fail-under=86
 # Coverage omit / report config lives in workspace/.coveragerc — coverage.py
 # only reads .coveragerc / setup.cfg / tox.ini / pyproject.toml, NOT
 # pytest.ini, so [coverage:*] sections here would be silently ignored.