Merge feature/late-entry-dsetup-throttle into tx_receipts

Bring in the 5s late-entry D-SETUP interval fix and return->continue
bug fix from the feature branch. Drop the mcch_queue_depth heuristic
throttle (StackState field, UMAC publish, CMCE check, dl_queue_depth)
in favor of the tx_receipt-based approach on this branch.

crates/tetra-entities/src/cmce/components/circuit_mgr.rs

@@ -8,7 +8,7 @@ use tetra_saps::{
 };
 
 const D_SETUP_REPEATS: i32 = 1;
-const LATE_ENTRY_INTERVAL_TIMESLOTS: i32 = multiframes!(20);
+const LATE_ENTRY_INTERVAL_TIMESLOTS: i32 = multiframes!(5);
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum CircuitErr {
@@ -307,7 +307,7 @@ impl CircuitMgr {
             tasks = self.close_expired_circuits(tasks);
 
             // Next, go through channels, see if D-SETUPs need to be sent
-            // Late entry: resend D-SETUP every 20 multiframes (5 seconds)
+            // Late entry: resend D-SETUP every 5 seconds
             for circuit in self.dl.iter() {
                 if let Some(circuit) = circuit {
                     let age = circuit.ts_created.age(dltime);
@@ -319,7 +319,7 @@ impl CircuitMgr {
                             .get_or_insert_with(Vec::new)
                             .push(CircuitMgrCmd::SendDSetup(circuit.call_id, circuit.usage, circuit.ts));
                     }
-                    // Late entry: resend every 20 multiframes
+                    // Late entry: resend every 5 seconds
                     else if age % LATE_ENTRY_INTERVAL_TIMESLOTS == 0 {
                         tasks
                             .get_or_insert_with(Vec::new)

crates/tetra-entities/src/cmce/subentities/cc_bs.rs

@@ -651,7 +651,7 @@ impl CcBsSubentity {
                         // Get our cached D-SETUP, build a prim and send it down the stack
                         let Some((pdu, dest_addr)) = self.cached_setups.get_mut(&call_id) else {
                             tracing::error!("No cached D-SETUP for call id {}", call_id);
-                            return;
+                            continue;
                         };
                         // Update transmission_grant based on current call state:
                         // During hangtime (nobody transmitting), use NotGranted;