feat: publish Tend v0.2 preview source

Publish the reviewed allowlisted snapshot whose exact binary completed maintenance deployment, rollback, and reactivation exercises for Gamertan and Sandwich Hime.

Private-Source-Commit: 4d7094c8b7c61991bfb67b11fc1558724c874eb2

Private-Source-Tree: 54a2f74804f7acddf3755d7d4da5b97f5fc28381

AI-Assistance: OpenAI Codex assisted implementation, testing, security review, and release verification.
Signed-off-by: Cole Speelman <crspeelman@gmail.com>

internal/deploy/lock_linux_test.go

@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+//go:build linux
+
+package deploy
+
+import (
+	"path/filepath"
+	"testing"
+)
+
+func TestHostWideLockSerializesIndependentServices(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "tend-deploy.lock")
+	first, err := acquireLock(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer first.Close()
+	if second, err := acquireLock(path); err == nil {
+		_ = second.Close()
+		t.Fatal("second service acquired the shared activation lock")
+	}
+	if err = first.Close(); err != nil {
+		t.Fatal(err)
+	}
+	third, err := acquireLock(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_ = third.Close()
+}