hive-c0re: spawn the auto-update and knowledge git calls through git_command

Three git spawns in workers/auto_update.rs and workers/knowledge.rs used
a bare tokio Command, so they ignored HYPERHIVE_GIT and, when the job
queue's deadline dropped their future (the knowledge pull has a 5 minute
one), the git child was left running instead of killed.

They now use lifecycle::git_command(), as the other git calls in
knowledge.rs already do.

hive-c0re/src/workers/auto_update.rs

@@ -51,7 +51,7 @@ pub fn current_flake_rev(hyperhive_flake: &str) -> Option<String> {
 /// starved the runtime and stalled the per-agent sockets.
 pub async fn agent_config_pending(name: &str, deployed_sha: Option<&str>) -> bool {
     let applied = crate::paths::applied_dir(name);
-    let applied_head = tokio::process::Command::new("git")
+    let applied_head = crate::lifecycle::git_command()
         .args(["-C", &applied.to_string_lossy(), "rev-parse", "HEAD"])
         .output()
         .await