media_delivery: fix SUPER_REPL spam + streaming verification

Bugs fixed:
- md_super_peer_add: timeout_tb = 0 → MEDIA_REPL_TIMEOUT_TB (timer fired every poll)
- md_repl_retrans_cb: md from peer->connect_timer (garbage) → peer->md
- md_repl_retrans_cb: removed inflight_count=0 reset (don't resend acked entries)
- stream_ctx: removed unused block_data field (was NULL, caused crash in BLOCK_DONE)

Test improvements:
- stream_completed flag for reliable streaming verification
- File created in <db_dir>/media/ (matches media_index path logic)
- 9/9 full test, 33/33 total

tests/test_media_delivery_full.c

@@ -235,17 +235,15 @@ static void phase_b1_file_transfer(void) {
     }
 
     TEST("n2→n1 BLOCK_REQ streams data"); {
-        fflush(stdout);
-        debug_set_level(DEBUG_LEVEL_TRACE);
         struct media_pkt_block_req req; memset(&req, 0, sizeof(req));
         req.subcmd = MEDIA_SUBCMD_BLOCK_REQ;
         memcpy(req.media_id, g_test_mid, 16); memcpy(req.block_id, g_test_bid0, 16);
         req.chunk = 0;
+        g_inst[0]->md.stream_completed = 0;
         msend(g_inst[1], g_nid[0], (const uint8_t*)&req, sizeof(req));
-        int a = 0, stream_was_active = 0;
-        while (a < 500) { uasync_poll(g_ua, POLL_MS); if (g_inst[0]->md.active_streams >= 1) stream_was_active = 1; a++; }
-        debug_set_level(DEBUG_LEVEL_ERROR);
-        if (stream_was_active) OK(); else FAIL("active_streams=%d after %dms", g_inst[0]->md.active_streams, 500 * POLL_MS);
+        int a = 0;
+        while (a < 2000 && !g_inst[0]->md.stream_completed) { uasync_poll(g_ua, POLL_MS); a++; }
+        if (g_inst[0]->md.stream_completed) OK(); else FAIL("stream not completed after %dms", 2000 * POLL_MS);
     }
 }