fix(ci): deflake redis lock test and covdata ETXTBSY race

- Raise the waiter timeout in TestStorageLocker_ObtainUsesProvidedContext
  from 25ms to 100ms. The whole notify chain (registration polling, lock
  release round-trip, pub/sub delivery) must fit in that window, which
  flaked on loaded CI runners. 100ms still stays below the minimum
  jittered fallback backoff (150ms), so the test keeps proving the
  notification path wakes the waiter.
- Pre-build go tool covdata in test workflows. Go builds it on demand
  into the build cache and go test -cover invokes it concurrently as
  packages finish; racing first builds intermittently fail with
  ETXTBSY (text file busy).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: mishushakov

.github/workflows/pr-tests-arm64.yml

@@ -173,6 +173,13 @@ jobs:
       - name: Install gotestsum
         run: go install gotest.tools/gotestsum@v1.13.0
 
+      # Go builds `go tool covdata` on demand into the build cache, and
+      # `go test -cover` invokes it concurrently as packages finish; racing
+      # first builds can fail with ETXTBSY ("text file busy"). Build it once
+      # up front so test-time invocations only exec the cached binary.
+      - name: Pre-build go tool covdata
+        run: go tool covdata >/dev/null 2>&1 || true
+
       - name: Compile test binaries
         working-directory: ${{ matrix.package }}
         run: sudo -E `which go` test -run '^$' ${{ matrix.test_path }}

.github/workflows/pr-tests.yml

@@ -122,6 +122,13 @@ jobs:
       - name: Install gotestsum
         run: go install gotest.tools/gotestsum@v1.13.0
 
+      # Go builds `go tool covdata` on demand into the build cache, and
+      # `go test -cover` invokes it concurrently as packages finish; racing
+      # first builds can fail with ETXTBSY ("text file busy"). Build it once
+      # up front so test-time invocations only exec the cached binary.
+      - name: Pre-build go tool covdata
+        run: go tool covdata >/dev/null 2>&1 || true
+
       # sudo strips PATH; pass it through so gotestsum/go resolve to the runner's
       # toolchain (1.26.3) instead of /usr/bin/go. Trap chowns reports back to
       # the runner so uploads can read them even when tests fail.

packages/api/internal/sandbox/storage/redis/lock_test.go

@@ -81,7 +81,11 @@ func TestStorageLocker_ObtainUsesProvidedContext(t *testing.T) {
 
 	waiterDone := make(chan error, 1)
 	go func() {
-		waiterLock, obtainErr := locker.Obtain(t.Context(), lockKey, 25*time.Millisecond)
+		// The timeout must stay below the minimum jittered fallback backoff
+		// (lockRetryMinInterval * (1 - lockRetryJitter) = 150ms) so the waiter
+		// can only succeed via the release notification, while leaving enough
+		// headroom for Redis round-trips and CI scheduling jitter.
+		waiterLock, obtainErr := locker.Obtain(t.Context(), lockKey, 100*time.Millisecond)
 		if obtainErr != nil {
 			waiterDone <- obtainErr