fix(Makefile): align test-race with CI configuration (#22727)

Follow-up to #22705 (pre-commit/pre-push hooks).

Unifies `test` and `test-race` into the same structure and lets CI call
`make test-race` instead of reproducing the gotestsum command.

**Parallelism**: Extracted from `GOTEST_FLAGS` into
`TEST_PARALLEL_PACKAGES`
/ `TEST_PARALLEL_TESTS` (default 8x8). `test-race` overrides to 4x4 via
target-specific Make variables. `TEST_NUM_PARALLEL_PACKAGES` and
`TEST_NUM_PARALLEL_TESTS` env vars continue to work for both targets.

**GOTEST_FLAGS**: Changed from simply-expanded (`:=`) to
recursively-expanded
(`=`) so target-specific overrides take effect at recipe time.

**CI**: `.github/actions/test-go-pg/action.yaml` now calls `make
test-race`
/ `make test` instead of hand-rolling the gotestsum command, eliminating
drift between local and CI configurations.

Refs #22705

.github/actions/test-go-pg/action.yaml

@@ -70,11 +70,7 @@ runs:
         set -euo pipefail
 
         if [[ ${RACE_DETECTION} == true ]]; then
-          gotestsum --junitfile="gotests.xml" --packages="${TEST_PACKAGES}" -- \
-            -tags=testsmallbatch \
-            -race \
-            -parallel "${TEST_NUM_PARALLEL_TESTS}" \
-            -p "${TEST_NUM_PARALLEL_PACKAGES}"
+          make test-race
         else
           make test
         fi

Makefile

@@ -1230,10 +1230,20 @@ else
 GOTESTSUM_RETRY_FLAGS :=
 endif
 
-# default to 8x8 parallelism to avoid overwhelming our workspaces. Hopefully we can remove these defaults
-# when we get our test suite's resource utilization under control.
-# Use testsmallbatch tag to reduce wireguard memory allocation in tests (from ~18GB to negligible).
-GOTEST_FLAGS := -tags=testsmallbatch -v -p $(or $(TEST_NUM_PARALLEL_PACKAGES),"8") -parallel=$(or $(TEST_NUM_PARALLEL_TESTS),"8")
+# Default to 8x8 parallelism to avoid overwhelming our workspaces.
+# Race detection defaults to 4x4 because the detector adds significant
+# CPU overhead. Override via TEST_NUM_PARALLEL_PACKAGES /
+# TEST_NUM_PARALLEL_TESTS.
+TEST_PARALLEL_PACKAGES := $(or $(TEST_NUM_PARALLEL_PACKAGES),8)
+TEST_PARALLEL_TESTS := $(or $(TEST_NUM_PARALLEL_TESTS),8)
+RACE_PARALLEL_PACKAGES := $(or $(TEST_NUM_PARALLEL_PACKAGES),4)
+RACE_PARALLEL_TESTS := $(or $(TEST_NUM_PARALLEL_TESTS),4)
+
+# Use testsmallbatch tag to reduce wireguard memory allocation in tests
+# (from ~18GB to negligible). Recursively expanded so target-specific
+# overrides of TEST_PARALLEL_* take effect (e.g. test-race lowers
+# parallelism).
+GOTEST_FLAGS = -tags=testsmallbatch -v -p $(TEST_PARALLEL_PACKAGES) -parallel=$(TEST_PARALLEL_TESTS)
 
 # The most common use is to set TEST_COUNT=1 to avoid Go's test cache.
 ifdef TEST_COUNT
@@ -1258,10 +1268,28 @@ endif
 
 TEST_PACKAGES ?= ./...
 
+# CI calls both test and test-race via .github/actions/test-go-pg/action.yaml.
 test:
-	$(GIT_FLAGS) gotestsum --format standard-quiet $(GOTESTSUM_RETRY_FLAGS) --packages="$(TEST_PACKAGES)" -- $(GOTEST_FLAGS)
+	$(GIT_FLAGS) gotestsum --format standard-quiet \
+		$(GOTESTSUM_RETRY_FLAGS) \
+		--packages="$(TEST_PACKAGES)" \
+		-- \
+		$(GOTEST_FLAGS)
 .PHONY: test
 
+test-race: TEST_PARALLEL_PACKAGES := $(RACE_PARALLEL_PACKAGES)
+test-race: TEST_PARALLEL_TESTS := $(RACE_PARALLEL_TESTS)
+test-race:
+	$(GIT_FLAGS) gotestsum --format standard-quiet \
+		--junitfile="gotests.xml" \
+		$(GOTESTSUM_RETRY_FLAGS) \
+		--packages="$(TEST_PACKAGES)" \
+		-- \
+		-race \
+		-timeout 30m \
+		$(GOTEST_FLAGS)
+.PHONY: test-race
+
 test-cli:
 	$(MAKE) test TEST_PACKAGES="./cli..."
 .PHONY: test-cli
@@ -1380,11 +1408,6 @@ test-postgres-docker:
 	done
 .PHONY: test-postgres-docker
 
-# Make sure to keep this in sync with test-go-race from .github/workflows/ci.yaml.
-test-race:
-	$(GIT_FLAGS) gotestsum --junitfile="gotests.xml" -- -tags=testsmallbatch -race -count=1 -parallel 4 -p 4 ./...
-.PHONY: test-race
-
 test-tailnet-integration:
 	env \
 		CODER_TAILNET_TESTS=true \