Harden the interop capture analysis and smppsim capture readiness (#89)

* Fail an interop run on an empty capture or a missing bind/bind_resp, and always tear down on analysis failure

* smppsim: wait for the capture sidecar to actually be capturing before node starts

* Clear the stale textdlr capture file too, and tidy the bind-check ordering

* Split the unlink comment so each line matches the unlink it explains

interop-tests/compose.smppsim.yaml

@@ -86,6 +86,13 @@ services:
       smppsim:
         condition: service_started
     command: ["dumpcap", "-i", "any", "-f", "tcp port 2775", "-w", "/captures/smppsim.pcapng"]
+    # dumpcap writes the pcapng section header as soon as it opens the interface, before any
+    # packet arrives, so a non-empty file means the capture is actually running.
+    healthcheck:
+      test: ["CMD-SHELL", "test -s /captures/smppsim.pcapng"]
+      interval: 1s
+      retries: 30
+      timeout: 2s
     volumes:
       - ./interop-tests/captures:/captures
 
@@ -101,15 +108,20 @@ services:
       smppsim-textdlr:
         condition: service_started
     command: ["dumpcap", "-i", "any", "-f", "tcp port 2775", "-w", "/captures/smppsim-textdlr.pcapng"]
+    healthcheck:
+      test: ["CMD-SHELL", "test -s /captures/smppsim-textdlr.pcapng"]
+      interval: 1s
+      retries: 30
+      timeout: 2s
     volumes:
       - ./interop-tests/captures:/captures
 
   node:
     depends_on:
       capture:
-        condition: service_started
+        condition: service_healthy
       capture-textdlr:
-        condition: service_started
+        condition: service_healthy
       smppsim:
         condition: service_healthy
       smppsim-textdlr: