Point agents at /agents/<name>/work and default subagents to it

The system prompt now names the work dir for worktrees, clones and build
trees, and keeps state/ for notes. A subagent started without a dir runs
in the agent's work dir instead of the daemon's own cwd.

hive-agent/src/prompt.rs

@@ -264,6 +264,12 @@ shared closer
         assert!(rendered.starts_with("You are hyperhive agent"));
     }
 
+    #[test]
+    fn render_points_agents_at_the_work_dir() {
+        let rendered = render(&PRODUCTION_TEMPLATE, "alice", "she/her", None, None, None);
+        assert!(rendered.contains("`/agents/alice/work/`"), "{rendered}");
+    }
+
     // Inline fixture for the {hive_identity} / {swarm_identity}
     // placeholders. Cargo's `cargo test` resolves `PRODUCTION_TEMPLATE`
     // against `$HIVE_ASSETS_DIR/prompts/system.md`, which the flake