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>

examples/server/services/example-site.json

@@ -0,0 +1,24 @@
+{
+  "schema_version": 2,
+  "service": { "name": "example-site", "allowed_host": "example.test", "environment_file": "/etc/tend/environment/example-site.env" },
+  "build": { "package": "./cmd/site", "binary": "example-site", "branch": "main" },
+  "deployment": {
+    "strategy": "singleton_candidate",
+    "root": "/opt/example-site",
+    "lock_file": "/run/lock/tend-deploy.lock",
+    "state_file": "/opt/example-site/tend-state.json",
+    "health_path": "/healthz",
+    "readiness_path": "/readyz",
+    "candidate_timeout_seconds": 30,
+    "smoke": [{ "path": "/", "contains": "Example site" }],
+    "public_smoke": [{ "url": "https://example.test/", "contains": "Example site" }],
+    "singleton": {
+      "unit": "example-site.service",
+      "address": "127.0.0.1:8092",
+      "candidate_address": "127.0.0.1:18092",
+      "listen_env": "EXAMPLE_LISTEN",
+      "current_link": "/opt/example-site/current",
+      "previous_link": "/opt/example-site/previous"
+    }
+  }
+}