docs: record wasm groundwork status + the 4 structural items remaining

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

ARCHITECTURE.md

@@ -468,9 +468,26 @@ multi-modal payloads (text inline, audio/photo/data via `iroh-blobs`). Receiving
 - [ ] Rotatable rooms/keys/identities + stable-handle directory indirection.
 - [ ] Private discovery (OPRF/PSI lookup; ZKP ownership proofs).
 - [ ] Capability model (UCAN); offline mailbox.
-- [ ] **Web client = `tethercore` on `wasm32`** — relay-only iroh peer, same
-      core, no server bridge. Gated on feature-gating the transports (iroh-only
-      build) + the IrohTransport (M4). A build target, not a project.
+- [~] **Web client = `tethercore` on `wasm32`** — relay-only iroh peer, same
+      core, no server bridge. (Correction: it's more *project* than *build
+      target* — see below.)
+      - [x] **Groundwork done** — deps are target-split: native-only transports
+            (tokio-net/mdns/webrtc) + UniFFI + native reqwest under
+            `cfg(not(wasm32))`; wasm gets minimal tokio + fetch-reqwest +
+            wasm-bindgen-futures + iroh (`default-features=false`). SSE/RTC/LAN
+            gated to native; getrandom wasm rng wired. `cargo build --target
+            wasm32-unknown-unknown --features iroh-transport` now reaches
+            tethercore's own code: **15 errors, 4 structural clusters.** Native
+            unaffected.
+      - [ ] **Decouple UniFFI** (10 errs) — the FFI macros are on every public
+            item; gate them out for wasm and add a `wasm-bindgen` surface instead.
+      - [ ] **iroh wasm feature set** (2 errs) — `default-features=false` strips
+            `presets::N0` / `iroh_gossip::net`; find the right wasm features.
+      - [ ] **Runtime** (1 err) — the engine builds a tokio multi-thread runtime;
+            wasm needs `spawn_local` + `?Send` futures (the real refactor — the
+            `Transport`/spawn signatures differ by target).
+      - [ ] **reqwest `.timeout()`** (1 err) — not on the fetch backend; cfg it out.
+      - [ ] Then `wasm-bindgen` + a JS shim; relay-only in-browser (no holepunch).
 - [ ] **Retire the Go server** once IrohTransport wins — replace with a
       self-hosted iroh-relay (supernode #1) + a tiny gossip-bootstrap rendezvous.