Merge branch 'fix/large-download-paths'

Concurrent-transfer limits, with the queue, the pause and the flag day.

A node now caps how many transfers it runs at once (8 downloads, 8 uploads,
node-wide) and how many one member may run in one group (2 by default,
operator-signed). Beyond that the node answers "queued" and the client waits its
turn, visibly, in the transfers panel — and a slot that frees starts whatever is
next, skipping past a member who is at their own cap rather than letting them
stall everyone behind them.

Browsing is never subject to a slot: not the poster grid, not the covers, not
opening a photo to look at it. That is structural — a transfer is what the
transfers widget shows — and the exemption is bounded rather than open, at two
files in flight per session, because an exemption with no bound is a leaseless
branch under another name.

Transfers can be cancelled, and now paused and resumed. A paused one holds
nothing: its slot goes back at once and resuming rejoins the queue at the tail.
Uploads survive the connection that started them and resume where the node
stopped, asked for inside the seal rather than on a clear message. What they
leave behind when they are abandoned is reaped, which closes a disk leak that
predates this work.

MNP 3.0 makes the lease compulsory and refuses 2.x at the handshake, with the
desktop client checking `client.minimum` before connecting so an un-updated one
says "update" instead of failing every connection in a protocol vocabulary.

Fourteen defects were found on the way, eight of them by a person clicking
Download and pasting a console — none of which 2075 tests could reach. Section
12 of ~/next/improve-downloads.md is that report, including the three this work
introduced itself and the one that turned out to be caused by an instruction to
hard-reload after each deployment.

Node suite 1209 passed, hub suite 866 passed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HCGdheDLxGReuKHga3BtST

1 files changed, 23 insertions, 2 deletions

diff --git a/packages/meshbay-hub/tests/harness/upload_seal_probe.mjs b/packages/meshbay-hub/tests/harness/upload_seal_probe.mjs
index 0b77e42..a6008c2 100644
--- a/packages/meshbay-hub/tests/harness/upload_seal_probe.mjs
+++ b/packages/meshbay-hub/tests/harness/upload_seal_probe.mjs
@@ -72,13 +72,34 @@ tp._nodeVersion = input.node_version;
 
 const frames = [];
 let uploadId = null;
+let answered = 0;
 tp._send = (msg) => {
   frames.push(toHex(msgpack_encode(msg)));
   if (msg.upload_id) uploadId = msg.upload_id;
-  if (input.mode !== 'receive') return;
+  if (input.mode !== 'receive') {
+    // Nothing answers in this mode -- except the probe, which the client waits
+    // five seconds for. A node that predates it refuses the index, and that
+    // refusal is a plain error rather than a sealed ack, so the harness can
+    // produce it honestly. It is also the degradation path worth exercising.
+    if (msg.chunk_index === -1) {
+      // With `probe_ack`, answer it the way a node holding part of this file
+      // does; without, the way one that predates the probe does.
+      const reply = input.probe_ack
+        ? Object.assign(msgpack_decode(hex(input.probe_ack)),
+                        { upload_id: uploadId })
+        : { type: 'error', upload_id: uploadId,
+            code: 'bad_chunk_index', detail: 'Unexpected chunk index' };
+      setImmediate(() => tp._dispatch(reply));
+    }
+    return;
+  }
   // Answer as the node did, on the next turn of the loop so the send path
   // finishes first — which is also how a real ack arrives.
-  const ack = msgpack_decode(hex(input.acks[msg.chunk_index]));
+  //
+  // By position, not by `chunk_index`: the node answers every frame including
+  // the probe, whose index is -1, and the two lists are built from the same
+  // sequence of frames.
+  const ack = msgpack_decode(hex(input.acks[answered++]));
   ack.upload_id = uploadId;
   // Through the real `_dispatch`, so the routing under test — matching an
   // ack to its uploader by `upload_id` — is the shipped one.