fix(quadlet): HealthCmd falls back to bash /dev/tcp before exit 0

The generated HealthCmd reported healthy (exit 0) whenever the image
shipped neither wget nor curl — btcpay-server sat 'healthy' in podman
ps while completely non-functional (live-testing report 2026-07-10).
Try a bash /dev/tcp connect to the health URL's host:port before
giving up; only images with none of wget/curl/bash still skip Podman
health (dropping exit 0 entirely would restart-loop those). Podman's
health timeout bounds the connect attempt.

Note: the rendered unit text changes, so every http-healthcheck app
gets a one-time unit rewrite + restart on first reconcile after this
binary lands.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

core/archipelago/src/container/quadlet.rs

@@ -538,13 +538,18 @@ fn translate_health_check(hc: &archipelago_container::HealthCheck) -> Option<Hea
                 format!("{url}{path}")
             };
             let helper_timeout = health_timeout_seconds(&hc.timeout);
+            let (tcp_host, tcp_port) = health_url_host_port(&final_url);
             // Images vary wildly: SearXNG ships wget but no curl, while some
-            // Node images ship neither. Use whichever probe helper exists and
+            // images (btcpay's dotnet base) ship neither but do have bash —
-            // skip Podman health if the image has none; host-side lifecycle
+            // fall through to a bash /dev/tcp connect probe there so the
-            // probes still verify reachability.
+            // container can't report healthy while its port is dead
+            // (btcpay-server, 2026-07-10). Podman's own health timeout bounds
+            // the connect attempt. Only images with none of the three skip
+            // Podman health entirely; host-side lifecycle probes still verify
+            // reachability for those.
             format!(
-                "if command -v wget >/dev/null 2>&1; then wget -q -T {1} -O /dev/null {0}; elif command -v curl >/dev/null 2>&1; then curl -fsS -m {1} {0}; else exit 0; fi",
+                "if command -v wget >/dev/null 2>&1; then wget -q -T {1} -O /dev/null {0}; elif command -v curl >/dev/null 2>&1; then curl -fsS -m {1} {0}; elif command -v bash >/dev/null 2>&1; then bash -c 'exec 3<>/dev/tcp/{2}/{3}'; else exit 0; fi",
-                final_url, helper_timeout
+                final_url, helper_timeout, tcp_host, tcp_port
             )
         }
         "cmd" => hc.endpoint.as_deref()?.to_string(),
@@ -558,6 +563,24 @@ fn translate_health_check(hc: &archipelago_container::HealthCheck) -> Option<Hea
     })
 }
 
+/// Host and port of an http(s) health URL, for the bash /dev/tcp fallback
+/// probe. Defaults to port 80/443 by scheme when the authority carries none.
+fn health_url_host_port(url: &str) -> (String, u16) {
+    let (default_port, rest) = if let Some(rest) = url.strip_prefix("https://") {
+        (443, rest)
+    } else {
+        (80, url.strip_prefix("http://").unwrap_or(url))
+    };
+    let authority = rest.split('/').next().unwrap_or(rest);
+    match authority.rsplit_once(':') {
+        Some((host, port)) => match port.parse::<u16>() {
+            Ok(port) => (host.to_string(), port),
+            Err(_) => (authority.to_string(), default_port),
+        },
+        None => (authority.to_string(), default_port),
+    }
+}
+
 fn health_timeout_seconds(raw: &str) -> u64 {
     let trimmed = raw.trim();
     if trimmed.is_empty() {
@@ -1459,7 +1482,22 @@ app:
         let h = translate_health_check(&http).expect("http must translate");
         assert_eq!(
             h.cmd,
-            "if command -v wget >/dev/null 2>&1; then wget -q -T 3 -O /dev/null http://localhost:8080/health; elif command -v curl >/dev/null 2>&1; then curl -fsS -m 3 http://localhost:8080/health; else exit 0; fi"
+            "if command -v wget >/dev/null 2>&1; then wget -q -T 3 -O /dev/null http://localhost:8080/health; elif command -v curl >/dev/null 2>&1; then curl -fsS -m 3 http://localhost:8080/health; elif command -v bash >/dev/null 2>&1; then bash -c 'exec 3<>/dev/tcp/localhost/8080'; else exit 0; fi"
+        );
+
+        // The /dev/tcp fallback must target the URL's host:port, with
+        // scheme-default ports when the authority carries none.
+        assert_eq!(
+            health_url_host_port("http://localhost:8080/health"),
+            ("localhost".to_string(), 8080)
+        );
+        assert_eq!(
+            health_url_host_port("http://127.0.0.1/"),
+            ("127.0.0.1".to_string(), 80)
+        );
+        assert_eq!(
+            health_url_host_port("https://localhost/status"),
+            ("localhost".to_string(), 443)
         );
 
         let cmdck = HealthCheck {