phase 5: wasm core, GalaxyClient skeleton, Connect-Web stubs

Compile `ui/core` to WebAssembly via TinyGo (903 KB) and expose four
canonical-bytes / signature-verification functions on
`globalThis.galaxyCore` from `ui/wasm/main.go`. The TypeScript-side
`Core` interface plus a `WasmCore` adapter (browser + JSDOM loader)
bridge those into a typed shape, and a `GalaxyClient` skeleton wires
`Core.signRequest` → injected `Signer` → typed Connect client →
`Core.verifyPayloadHash` / `verifyResponse`.

Wire `ui/buf.gen.yaml` against the local
`@bufbuild/protoc-gen-es` v2 binary (devDependency) so the codegen
step does not depend on the buf.build BSR. Vitest covers the bridge
end-to-end: per-method WasmCore tests under JSDOM, byte-for-byte
canon parity against the gateway fixtures committed in Phase 3, and
a `GalaxyClient` orchestration test using
`createRouterTransport`. The committed `core.wasm` snapshot tracks
TinyGo output so contributors run `make wasm` only when `ui/core/`
changes; CI consumes the snapshot directly.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

ui/README.md

@@ -56,7 +56,30 @@ under `ui/docs/` as they are introduced.
 
 ## Repository layout
 
-Filled in incrementally as phases land. Today only `frontend/` exists.
+```text
+ui/
+├── PLAN.md                 staged implementation plan (Phases 1-36)
+├── Makefile                wasm / ts-protos / web / mobile / desktop targets
+├── README.md               this file
+├── buf.gen.yaml            local-plugin TS Protobuf-ES generator
+├── docs/                   topic-based design notes
+│   ├── testing.md          per-PR / release test tiers
+│   └── wasm-toolchain.md   TinyGo build, JSDOM loading, bundle budget
+├── core/                   ui/core Go module (canonical bytes, keypair)
+├── wasm/                   TinyGo entry point exposing Core to JS
+└── frontend/               SvelteKit / Vite source
+    ├── src/api/            GalaxyClient + typed Connect client
+    ├── src/platform/core/  Core interface + WasmCore adapter
+    ├── src/proto/          generated Protobuf-ES + Connect descriptors
+    └── static/             core.wasm + wasm_exec.js (committed artefacts)
+```
+
+Linked topic docs:
+
+- [`docs/wasm-toolchain.md`](docs/wasm-toolchain.md) — TinyGo build,
+  loading recipe, bundle size budget.
+- [`docs/testing.md`](docs/testing.md) — Tier 1 per-PR + Tier 2
+  release test tiers.
 
 ```text
 ui/