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/blue-green/example-site@.service

@@ -6,7 +6,8 @@ After=network.target
 Type=simple
 DynamicUser=yes
 ExecStart=/opt/example-site/slots/%i/example-site
-EnvironmentFile=/etc/example-site/%i.env
+EnvironmentFile=/etc/tend/environment/example-site.env
+EnvironmentFile=/etc/tend/slots/example-site-%i.env
 NoNewPrivileges=yes
 PrivateTmp=yes
 ProtectSystem=strict

examples/blue-green/tend.json

@@ -1,16 +1,17 @@
 {
-  "schema_version": 1,
-  "service": { "name": "example-site", "allowed_host": "example.test" },
+  "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": "blue_green",
     "root": "/opt/example-site",
-    "lock_file": "/run/lock/gamertan-deploy.lock",
+    "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" }],
     "blue_green": {
       "caddy_config": "/etc/caddy/Caddyfile",
       "caddy_handler": "/etc/caddy/example-site-handler.caddy",