perf(ci): add -n auto to CI pytest + fix coverage combining (#388)

The earlier xdist attempt was reverted in 847713d because pytest-cov
combined results unreliably under -n auto. Root cause: missing
[tool.coverage.run] parallel=true in pyproject.toml. Without it,
each worker overwrites .coverage atomically and the report drops
data from all but one worker.

Fix:
- pyproject.toml: add [tool.coverage.run] with parallel=true,
  source=["src"], concurrency=["multiprocessing","thread"]. Verified
  locally: 56-test xdist run produces a clean combined coverage
  report at 99% (vs flaky/missing data before).
- dev/scripts/backends/gitea.py + github.py: add -n auto to the
  emitted pytest command. Also persist the deploy.yml report-step
  failure gate (was applied to the file in 5f826f6 but the emitter
  itself didn't have it, so regen would strip it).
- .gitea/workflows/ci.yml: regenerated to pick up -n auto.

The 32-core runner should now run CI pytest in roughly 1/Nth the
prior time (where N is bounded by serialization on slow tests).

Phase 1 of #388 (pre-commit hook xdist) shipped in 49f004a.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -47,7 +47,11 @@ jobs:
         run: uv sync --dev
 
       - name: Pytest
-        run: uv run pytest tests/ -x --cov=src --cov-report=term-missing --cov-fail-under=99 -q
+        # -n auto parallelizes across runner cores. Coverage combining
+        # is configured via [tool.coverage.run] parallel=true in
+        # pyproject.toml — without that the per-worker .coverage.* files
+        # don't merge reliably (see #388 for the prior revert).
+        run: uv run pytest tests/ -x --cov=src --cov-report=term-missing --cov-fail-under=99 -q -n auto
 
       - name: File failure issue
         if: failure()

dev/scripts/backends/gitea.py

@@ -178,7 +178,11 @@ jobs:
         run: uv sync --dev
 
       - name: Pytest
-        run: uv run pytest tests/ -x --cov=src --cov-report=term-missing --cov-fail-under={coverage_threshold} -q
+        # -n auto parallelizes across runner cores. Coverage combining
+        # is configured via [tool.coverage.run] parallel=true in
+        # pyproject.toml — without that the per-worker .coverage.* files
+        # don't merge reliably (see #388 for the prior revert).
+        run: uv run pytest tests/ -x --cov=src --cov-report=term-missing --cov-fail-under={coverage_threshold} -q -n auto
 
 {_failure_step("CI", "test")}
 """
@@ -266,6 +270,10 @@ jobs:
 {_setup_uv_step(uv_version)}
 
       - name: Report
+        # Only file an issue if at least one upstream build job failed.
+        # Without this gate api.diag.ci runs unconditionally and files
+        # a fake "failed" issue on every successful Deploy run.
+        if: contains(needs.*.result, 'failure')
         env:
           GITEA_TOKEN: ${{{{ secrets.DEPLOY_TOKEN }}}}
         run: |

dev/scripts/backends/github.py

@@ -159,7 +159,9 @@ jobs:
         run: uv run ruff format --check src/ tests/
 
       - name: Pytest
-        run: uv run pytest tests/ --cov=src --cov-report=term-missing --cov-fail-under={coverage_threshold} -q
+        # -n auto parallelizes across runner cores; pytest-cov combines
+        # results via [tool.coverage.run] parallel=true in pyproject.toml.
+        run: uv run pytest tests/ --cov=src --cov-report=term-missing --cov-fail-under={coverage_threshold} -q -n auto
 
       - name: Validate generated config
         run: uv run python dev/scripts/gen_config.py --check

pyproject.toml

@@ -187,6 +187,14 @@ markers = [
     "stub: marks tests that report stub vs implemented status (deselect with '-m \"not stub\"')",
 ]
 
+[tool.coverage.run]
+# Required for reliable pytest-cov + pytest-xdist combining: each worker
+# writes .coverage.<host>.<pid>, then pytest-cov auto-combines at exit.
+# Without this, parallel test runs randomly drop coverage data.
+parallel = true
+source = ["src"]
+concurrency = ["multiprocessing", "thread"]
+
 [tool.uv.build-backend]
 module-name = ["aco", "api", "bcda", "bib", "bls", "ccw", "cli", "cms", "conf", "mail", "opps", "perf", "pfs", "prisma", "rec", "rex", "sem"]
 namespace = true