merge: Phase 11.5 security remediation, invite redesign, per-node identity

Brings in the security remediation branch. Three bodies of work, and what they
changed about what this project may claim.

Phase 11.5 closed the gap between the documents and the code: the unauthenticated
node HTTP API and the TCP transport deleted, one handshake shared by the
remaining two transports, mutual authentication, structured admin transcripts,
upload confinement, group isolation, revocation that reaches nodes. Six critical
and seven high findings closed, bounded, or deferred by decision.

The invite redesign closed H3 and M3 — the last open High. The hub was the key
directory: an inviter fetched the invitee's key from it and wrapped the group key
for whatever came back, so a hub answering with its own key was handed the group
key by an honest member following the protocol exactly. That lookup is gone. The
node holds the group key and wraps it itself, for a key its recipient proves
possession of, bound to an account by a one-time code the hub never sees. M3 fell
out of the same work: node authority comes from a local roster, never from the
hub.

Per-node identity cut what remains of C4 down to one operator. A single keypair
used to be copied to every node its owner joined; each node now gets its own, so
cracking the bundle on one machine yields a key that is a stranger everywhere
else — and on that machine, one that unlocks nothing its holder did not already
serve. The bundle KDF moved to Argon2id 128 MB, and the hub stopped storing or
publishing user keys at all.

What this project may now say: the hub cannot read your content unless it ships
you malicious client code. T3 remains, accepted (D1), and is what the native
client removes. C4 is reduced, not closed, until 13.3. Chat is still plaintext at
rest until Phase 15. Draft-v5 §2 states each claim against the adversary it holds
against, which is the convention this branch exists to keep.

Four defects were found by deploying it and using a browser, none by the test
suite: a node going deaf on its hub socket, a token that predated group
membership, a client reading values before they were assigned, and identity keys
a browser held but never re-read. The lessons are recorded in CLAUDE.md.

Tests: 343 across the three packages, plus QE/deploy/e2e.py — register, pair,
invite, join, download, stream, second browser, revoke — run against the live
deployment on a wiped hub and node.

1 files changed, 103 insertions, 0 deletions

diff --git a/packages/meshbay-hub/tests/test_spa_ordering.py b/packages/meshbay-hub/tests/test_spa_ordering.py
new file mode 100644
index 0000000..0ef34fc
--- /dev/null
+++ b/packages/meshbay-hub/tests/test_spa_ordering.py
@@ -0,0 +1,103 @@
+"""
+Ordering guards for the SPA's connect() flow.
+
+These are source-level checks, which is not how one would normally test
+behaviour. They exist because a specific class of bug shipped to a live browser
+twice and no other test could see it: `connect()` is a long sequence in which
+later steps read values earlier steps set, and the Python end-to-end client in
+QE/deploy/ cannot catch a mistake there — it is a different implementation,
+written in the right order by construction, so it passes while the browser fails.
+
+Concretely: join_request signs a transcript over the node key and the node nonce,
+and runs *before* the GEK proof, because a first-time member has no GEK to prove.
+Both values were being read further down, next to the proof that also uses them,
+so every invited member hit "Handshake incomplete — reconnect and retry".
+
+If you restructure connect(), these will fail. Check the invariant still holds —
+that nothing reads a value assigned later — and then move the markers.
+"""
+
+from pathlib import Path
+
+import pytest
+
+STATIC = (Path(__file__).resolve().parents[1]
+          / "src" / "meshbay_hub" / "static")
+TRANSPORT = STATIC / "transport.js"
+
+pytestmark = pytest.mark.skipif(
+    not TRANSPORT.exists(), reason="SPA sources not present")
+
+
+def _positions(*needles: str) -> list[int]:
+    source = TRANSPORT.read_text()
+    out = []
+    for needle in needles:
+        idx = source.find(needle)
+        assert idx != -1, f"{needle!r} is gone from transport.js — update this test"
+        out.append(idx)
+    return out
+
+
+def test_challenge_values_are_captured_before_joining():
+    """
+    joinGroup() signs over node_pk and nonce_node, so both must be recorded when
+    the challenge arrives — not later, beside the proof.
+    """
+    # Deliberately loose markers: what matters is where the assignment happens,
+    # not how it is spelled, so a reordering fails on the ordering assertion
+    # below rather than on a missing string.
+    node_pk, nonce_node, join_call = _positions(
+        "this.nodePk = reply.node_pk",
+        "this._nonceNode = ",
+        "await this.joinGroup(",
+    )
+    assert node_pk < join_call, (
+        "node_pk is read from the challenge after joinGroup() runs — the join "
+        "would sign a transcript naming nothing")
+    assert nonce_node < join_call, (
+        "nonce_node is captured after joinGroup() runs — the join would not be "
+        "bound to this connection")
+
+
+def test_join_happens_before_the_gek_proof():
+    """
+    The whole point of joining in the pre-proof window: someone who has never
+    held the group key cannot produce a proof, so the key has to arrive first.
+    """
+    join_call, proof = _positions(
+        "await this.joinGroup(",
+        "await C.handshakeProof(",
+    )
+    assert join_call < proof, (
+        "the join must happen before the GEK proof — a first-time member has no "
+        "key to prove with")
+
+
+def test_keys_are_recovered_before_the_join_is_attempted():
+    """
+    A second browser holds nothing but a password. It recovers its identity keys
+    from the node's encrypted keypair bundle, and only then can it sign a join —
+    so the recovery has to come first. Getting this order wrong is invisible on
+    the browser that registered, and breaks every other one.
+    """
+    recover, join_call = _positions(
+        "type: 'keypair_bundle_fetch'",
+        "await this.joinGroup(",
+    )
+    assert recover < join_call, (
+        "the keypair bundle must be fetched before joinGroup() — otherwise a "
+        "browser that did not register has no key to sign the join with")
+
+
+def test_the_ack_still_verifies_the_announced_node_key():
+    """
+    Taking node_pk from the challenge is only safe because the ack proves it and
+    the client compares the two. Losing that check would leave the announcement
+    trusted on its own.
+    """
+    source = TRANSPORT.read_text()
+    assert "Node identity changed during the handshake" in source, (
+        "the challenge's node_pk must be checked against the ack's")
+    assert "verifyNodeSignature" in source, (
+        "the ack's signature over the handshake transcript must still be verified")