fix(rtmp): avoid segfault on connection-refused teardown

Track libavformat RTMP session initialization state so teardown only writes a trailer after the muxer header succeeds. This avoids calling av_write_trailer() on partially initialized sessions when avio_open2() fails with Connection refused.

Add a fault-suite regression for libavformat RTMP connection refusal and update the summary helper to compute all_pass from the actual manifest size instead of a hardcoded seven-row expectation.

Verified by rebuilding cvmmap_streamer and rtmp_output_tester, reproducing the refused-connection path without a crash, and running ./scripts/fault_suite.sh successfully (8/8).

scripts/fault_suite.sh

@@ -238,6 +238,18 @@ EOF
 		--frame-interval-ms 1 \
 		--linger-ms 0
 
+	run_expected_failure 8 "libavformat_connection_refused" "libavformat connection refusal surfaces without crashing" \
+		"failed to open RTMP output 'rtmp://127.0.0.1:1/live/test': Connection refused" \
+		"${RTMP_OUTPUT_TESTER}" \
+		--rtmp-url rtmp://127.0.0.1:1/live/test \
+		--transport libavformat \
+		--codec h264 \
+		--frames 1 \
+		--width 320 \
+		--height 240 \
+		--frame-interval-ms 1 \
+		--linger-ms 0
+
 	local finished_at_utc
 	finished_at_utc="$(date -u +"%Y-%m-%dT%H:%M:%SZ")"
 
@@ -294,7 +306,7 @@ PY
 		echo "counts_pass=${pass_count}"
 		echo "counts_fail=${fail_count}"
 		echo "all_pass=${all_pass}"
-		echo "scenarios=removed_encoder_backend,removed_rtmp_transport,removed_rtmp_mode_cli,removed_rtmp_mode_toml,missing_rtmp_url,invalid_rtp_endpoint,ffmpeg_process_bad_binary"
+		echo "scenarios=removed_encoder_backend,removed_rtmp_transport,removed_rtmp_mode_cli,removed_rtmp_mode_toml,missing_rtmp_url,invalid_rtp_endpoint,ffmpeg_process_bad_binary,libavformat_connection_refused"
 	} > "${EVIDENCE_TEXT}"
 
 	if [[ "${all_pass}" == "true" ]]; then