Run Bazel CI locally without BuildBuddy credentials (#59055)

## What changed

- Remove automatic BuildBuddy configuration and credential forwarding from Bazel CI, release, SDK, and voice builds. Strip remote execution CI configs in the shared wrapper while retaining explicit remote configurations for local use.
- Use native Windows host tools and audio dependencies for Windows Bazel actions, forwarding the required toolchain and environment settings.
- Initialize message-board MCP servers through a per-session `OnceCell` so server startup does not hold the shared registry lock across an await.
- Expose the message-board test helper to the core Bazel package and update the runtime-auth test call for the `reauth` argument.

GitOrigin-RevId: 5d5c1f4d71fa841090dea8eec8006380981fb65b

.github/scripts/test_rusty_v8_bazel.py

@@ -72,7 +72,7 @@ class RustyV8BazelTest(unittest.TestCase):
             with patch.object(rusty_v8_bazel, "MODULE_BAZEL", module_bazel):
                 self.assertEqual("146.4.0", rusty_v8_bazel.command_version(None))
 
-    def test_bazel_commands_use_shared_buildbuddy_remote_config_library(self) -> None:
+    def test_bazel_commands_use_shared_ci_options(self) -> None:
         with patch.dict(environ, {}, clear=True):
             self.assertEqual(
                 [
@@ -86,22 +86,6 @@ class RustyV8BazelTest(unittest.TestCase):
                     "//third_party/v8:release",
                 ),
             )
-        with patch.dict(environ, {"BUILDBUDDY_API_KEY": "token"}, clear=True):
-            self.assertEqual(
-                [
-                    "bazel",
-                    "build",
-                    "--config=buildbuddy-generic-rbe",
-                    "--remote_header=x-buildbuddy-api-key=token",
-                    "--config=ci-v8",
-                    "//third_party/v8:release",
-                ],
-                rusty_v8_bazel.bazel_command(
-                    "build",
-                    "--config=ci-v8",
-                    "//third_party/v8:release",
-                ),
-            )
 
     def test_release_pair_labels_and_staged_names_distinguish_sandbox_artifacts(
         self,