CB-564: give a voice to silent member-failure paths

Injector.drop, CompletionResolver.fail, SessionManager.onFailed/reapIdle/
acquire spawn failures, and MessageService.abandon used to fail a member
or a caller's request with no log, a bare DEBUG, or a log that named only
the symptom ("session marked failed", "failed send via turn-stall
fallback"). Each now logs at WARN and names the real cause and the
numbers involved. Observability only — no behaviour changed.

bridged/src/main/java/dev/ltms/bridged/inject/CompletionResolver.java

@@ -200,7 +200,7 @@ public final class CompletionResolver implements TurnListener {
         }
         if (rendezvous.resolveFailure(waiter, reason)) {
             inFlight.remove(target, turn);
-            log.debug("failed send to {} via turn-stall fallback", target);
+            log.warn("failing send to {} via turn-stall fallback: {}", target, reason);
         }
     }
 

bridged/src/main/java/dev/ltms/bridged/inject/Injector.java

@@ -402,6 +402,10 @@ public final class Injector {
             t.awaitingPostTurnPickup = false;
             t.postTurnObserved = false;
         }
+        log.warn("{} is gone, dropping its queue: {} message(s) failed{}; cause: {}", target,
+                pending.size(),
+                hadDeliveredTurn ? " (including one turn already in flight whose completion was never confirmed)" : "",
+                cause.getMessage());
         forget.accept(target); // the worker is gone — clear its readiness/presence too (CB-114)
         for (Pending p : pending) {
             p.delivered().completeExceptionally(cause);

bridged/src/main/java/dev/ltms/bridged/msg/MessageService.java

@@ -277,7 +277,7 @@ public final class MessageService {
         }
         boolean failed = rendezvous.resolveFailure(waiter, reason);
         if (failed) {
-            log.debug("abandoned send to {}: {}", target, reason);
+            log.warn("abandoning the blocked send to {}: {}", target, reason);
         }
         return failed;
     }

bridged/src/main/java/dev/ltms/bridged/session/SessionManager.java

@@ -141,7 +141,13 @@ public final class SessionManager implements TurnListener {
             // to pick the profile out of that role's pool and to label the tab; a role kept only on
             // the MemberSession is recorded after the spawn it was supposed to steer.
             SpawnRequest req = new SpawnRequest(profile, requestedCwd, callerCwd, null, null, memberRole);
-            PeerHandle handle = launcher.spawn(req);
+            PeerHandle handle;
+            try {
+                handle = launcher.spawn(req);
+            } catch (RuntimeException e) {
+                log.warn("spawn failed for profile={} role={}: {}", profile, memberRole, e.getMessage());
+                throw e;
+            }
             String resolvedProfile = resolveProfile(handle, profile);
             String cwd = launcher.effectiveCwd(new SpawnRequest(resolvedProfile, requestedCwd, callerCwd));
             long now = nowNanos.getAsLong();
@@ -313,6 +319,8 @@ public final class SessionManager implements TurnListener {
             worktrees.overlayParity(repoRoot, path, launcher.parityOverlay(preResolvedProfile));
             handle = launcher.spawn(new SpawnRequest(profile, path, callerCwd, null, null, memberRole));
         } catch (RuntimeException e) {
+            log.warn("spawn failed for profile={} role={} branch={} path={}: {}",
+                    preResolvedProfile, memberRole, branch, path, e.getMessage());
             if (path != null) {
                 try {
                     worktrees.remove(repoRoot, path);
@@ -498,8 +506,10 @@ public final class SessionManager implements TurnListener {
         MemberSession current = findByTerminal(target);
         if (current == null) return;
         if (current.state() == MemberSession.State.RELEASED) return;
+        MemberSession.State priorState = current.state();
         if (replace(current, current.withState(MemberSession.State.FAILED))) {
-            log.debug("session marked failed terminal={} pane={}", target, current.paneId());
+            log.warn("member terminal={} pane={} can no longer be delegated to: its turn never resolved "
+                    + "(was {} when it failed)", target, current.paneId(), priorState);
         }
     }
 
@@ -515,7 +525,11 @@ public final class SessionManager implements TurnListener {
             if (s.state() != MemberSession.State.READY && s.state() != MemberSession.State.DONE) {
                 continue;
             }
-            if (now - s.lastActivityAtNanos() > idleTtlNanos) {
+            long idleNanos = now - s.lastActivityAtNanos();
+            if (idleNanos > idleTtlNanos) {
+                log.debug("reaping idle session terminal={} pane={}: idle {}s exceeds the {}s ttl",
+                        s.terminalId(), s.paneId(), TimeUnit.NANOSECONDS.toSeconds(idleNanos),
+                        TimeUnit.NANOSECONDS.toSeconds(idleTtlNanos));
                 release(s.paneId());
                 reaped++;
             }