fix(beads): align agent bead prefixes and force multi-hyphen IDs (#482)

* fix(beads): align agent bead prefixes and force multi-hyphen IDs

* fix(checkpoint): treat threshold as stale at boundary

internal/beads/force.go

@@ -0,0 +1,11 @@
+package beads
+
+import "strings"
+
+// NeedsForceForID returns true when a bead ID uses multiple hyphens.
+// Recent bd versions infer the prefix from the last hyphen, which can cause
+// prefix-mismatch errors for valid system IDs like "st-stockdrop-polecat-nux"
+// and "hq-cv-abc". We pass --force to honor the explicit ID in those cases.
+func NeedsForceForID(id string) bool {
+	return strings.Count(id, "-") > 1
+}