fix(#2676): stop hive-priv flooding the journal with list output

`container_run` logs every stdout line at INFO (target `nixos-container`)
as operation progress. For the read-only `list` op — called on the hot
path (dashboard rescan, forge + boot sweeps) — that stdout is the return
value, not progress, so every call logs the full ~28-line container roster
at INFO. hive-c0re calls it several times a second, flooding the host
journal.

Gate the stdout per-line INFO logging on the op not being `list`. Mutating
ops still log their progress; stderr is still logged for every op (errors
matter regardless). No behaviour change beyond log volume.

hive-priv/src/main.rs

@@ -1419,8 +1419,15 @@ async fn container_run(args: &[&str]) -> Result<(String, String)> {
         .context("invoke nixos-container")?;
     let stdout = String::from_utf8_lossy(&out.stdout).into_owned();
     let stderr = String::from_utf8_lossy(&out.stderr).into_owned();
-    for line in stdout.lines() {
-        tracing::info!(target: "nixos-container", "{line}");
+    // `list` is a read-only enumeration called on the hot path (dashboard
+    // rescan, forge + boot sweeps) — its stdout is the return value, not
+    // progress, so logging every container name on every call floods the
+    // journal. Log stdout only for the mutating ops, where each line is
+    // genuine progress. stderr is always logged (errors matter regardless).
+    if args.first() != Some(&"list") {
+        for line in stdout.lines() {
+            tracing::info!(target: "nixos-container", "{line}");
+        }
     }
     for line in stderr.lines() {
         tracing::warn!(target: "nixos-container", "{line}");