roll: pigweed pw_async2: Experimental Future type

Defines a standard `Future` interface for a pending asynchronous
operation. This is experimental and should not be used until stable.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/321172
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>
Original-Revision: 3959870dd94ecd688c531544a32b71bb8efe1101

Rolled-Repo: https://pigweed.googlesource.com/pigweed/pigweed
Rolled-Commits: 2fb733cb5103f9..3959870dd94ecd
Roll-Count: 1
Roller-URL: https://cr-buildbucket.appspot.com/build/8703002230006489281
GitWatcher: ignore
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I8f46fb462185ccc7659b8d89766360752207b0d0
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/quickstart/bazel/+/324456
Bot-Commit: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Commit-Queue: Pigweed Roller <pigweed-roller@pigweed-service-accounts.iam.gserviceaccount.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
diff --git a/MODULE.bazel b/MODULE.bazel
index 01d7556..b6b3fa2 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -41,9 +41,9 @@
 git_override(
     module_name = "pigweed",
     # ROLL: Warning: this entry is automatically updated.
-    # ROLL: Last updated 2025-09-21.
-    # ROLL: By https://cr-buildbucket.appspot.com/build/8703112571209059281.
-    commit = "2fb733cb5103f98af81d2bfedfd55e2eca7a8d52",
+    # ROLL: Last updated 2025-09-22.
+    # ROLL: By https://cr-buildbucket.appspot.com/build/8703002230006489281.
+    commit = "3959870dd94ecd688c531544a32b71bb8efe1101",
     remote = "https://pigweed.googlesource.com/pigweed/pigweed",
 )