docs: draft-v5 architecture spec

Supersedes draft-v4, which described a system the code did not implement and
made several claims that were simply wrong — "ALL operations require the GEK
proof" (true on one of four transports), "Argon2id 256 MB" (hub only), "hub
stores no content metadata" (private file hashes were registered with it).

Written as a delta over v4: sections not restated are unchanged. Carries an
explicit rule — a claim must name the adversary it holds against — and a
per-adversary table replacing v4's informal assurances.

Records the decisions: transport (aiortc primary, QUIC retained, TCP and the
node HTTP API removed), unified handshake with mutual authentication, admin
operation transcripts, node authority over GEK storage and activation, upload
confinement, hub node-registration and signaling authorization, and the client
architecture — hub keeps serving the web SPA, native client offered alongside,
hub minimization deferred.

States plainly what is NOT true. The defensible claim is "the hub cannot read
your content unless it actively attacks you", not "unreadable by other parties,
even the hub": H3 (hub is the key directory and can substitute a key at invite
time) is open until Phase 12.1, and T3 (hub serves the SPA) is accepted
permanently by decision. Content is also readable by every group member and by
the node operator, so "end-to-end" here means client-to-node, never
client-to-client.

Corrects the v4 NAT traversal account: punch_nat() is a single UDP probe with
no STUN, no candidate gathering and no fallback, validated on one ISP. ICE is
the traversal path, including for native clients.

Open items listed with status, including C6 on the QUIC path.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

0 files changed, 0 insertions, 0 deletions