test(e2e-stress): fix stale sub-64KB comments after multi-fragment extension

Test/E2E/chain/stress.py

@@ -134,11 +134,11 @@ def _gate(min_frames=5, marte_rss=512.0, hub_rss=1024.0, zoom_p95=1000.0):
 # Single source + single hub; the load lands on the UDPStreamer serialise/send
 # path and is read back through one WS client (proc_perf measures marte).
 
-# size: one float32 array, growing element count → bigger single-datagram packet.
+# size: one float32 array, growing element count → bigger packet.
 _DS_SIZE = [
     mk_stress(f"ds_size_{e}", "ds_signal_elements", e,
               [_source("src", 1, e)], gate=_gate())
-    for e in (1000, 4000, 8000, 15000)   # 4 KB → 60 KB packets (sub-64 KB cap)
+    for e in (1000, 4000, 8000, 15000)   # 4 KB → 60 KB packets (original single-datagram cases)
 ]
 
 # Multi-fragment size cases: one float32 array large enough that the DATA packet
@@ -162,7 +162,7 @@ _DS_SIZE += [
 _DS_COUNT = [
     mk_stress(f"ds_count_{n}", "ds_signal_count", n,
               [_source("src", n, 1000)], gate=_gate())
-    for n in (1, 4, 8, 15)   # 15*4 KB ≈ 60 KB packet (sub-64 KB cap)
+    for n in (1, 4, 8, 15)   # 15*4 KB ≈ 60 KB packet (original single-datagram case)
 ]
 
 # clients (fan-out): one source, M subscriber hubs (ds_fanout shape). The
@@ -231,8 +231,9 @@ def validate_case(c):
                         f"(UDPStreamer max unicast clients)")
     if c["shape"] == "hub" and (st["clients"] < 1):
         errs.append(f"{c['id']}: hub clients must be >= 1")
-    # Single-datagram ceiling: keep each source's packet < 64 KB so it never
-    # needs reassembly (the deliverable-packet cap).
+    # Enforce 1 MiB deliverable cap (UDPS_CLIENT_MAX_PACKET_BYTES): each source's
+    # reassembled DATA payload must stay under this. Note: the size axis includes
+    # multi-fragment cases that intentionally exceed 64 KB (reassembled by UDPSClient).
     for src in c["sources"]:
         n_data = sum(1 for s in src["signals"] if not s["is_time"])
         elem = max((s["elements"] for s in src["signals"]