fix(queue): rename queued_ids to active_ids, document circular-dep caveat

docs/coordinator.md

@@ -96,6 +96,11 @@ each entry finishes. When a dep entry transitions to terminal, the loop re-evalu
 the queue immediately, so downstream entries are unblocked with no extra wakeup. No
 additional `notify_one()` call is needed.
 
+**Circular-dep caveat**: if A depends on B and B depends on A, neither entry ever
+becomes runnable — the worker skips both indefinitely with no error. Callers must
+ensure acyclic dep graphs. Cycle detection is deferred to a future iteration (when
+parallel workers make a stuck queue more visible).
+
 ---
 
 ## Container view

hive-c0re/src/rebuild_queue.rs

@@ -468,9 +468,10 @@ impl RebuildQueue {
             .filter(|e| e.state.is_terminal())
             .map(|e| e.id)
             .collect();
-        // All queued ids — used to distinguish "not yet terminal" from
-        // "evicted (= resolved)".
-        let queued_ids: std::collections::HashSet<u64> = inner
+        // Active (non-terminal) ids: Queued + Running. Named `active_ids`
+        // rather than `queued_ids` because Running entries are included;
+        // used to distinguish "still in flight" from "evicted (= resolved)".
+        let active_ids: std::collections::HashSet<u64> = inner
             .entries
             .iter()
             .filter(|e| !e.state.is_terminal())
@@ -480,7 +481,11 @@ impl RebuildQueue {
             e.state == QueueState::Queued
                 && e.depends_on.iter().all(|dep_id| {
                     // Resolved if terminal in queue OR not in queue at all.
-                    terminal_ids.contains(dep_id) || !queued_ids.contains(dep_id)
+                    // Note: circular deps (A depends on B, B depends on A)
+                    // silently deadlock — neither entry ever becomes runnable.
+                    // Not a problem in v1 (no callers yet), but callers must
+                    // ensure acyclic dep graphs.
+                    terminal_ids.contains(dep_id) || !active_ids.contains(dep_id)
                 })
         })?;
         let entry = &mut inner.entries[pos];