feat(wasm-mps): add --target web build for browser-safe WASM init

Add dist/web/js/wasm Makefile target using wasm-pack --target web,
which generates an explicit async init() default export. Callers
await init() before using any WASM function, eliminating the webpack
asyncWebAssembly timing race that left wasm undefined.

Export the build via the ./web subpath export so consumers can import
directly from @bitgo/wasm-mps/web.

Ticket: WCI-250

Author: Marzooqa

packages/wasm-mps/Makefile

@@ -64,6 +64,10 @@ dist/esm/js/wasm:
 dist/cjs/js/wasm:
 	$(call BUILD,$@,nodejs)
 
+.PHONY: dist/web/js/wasm
+dist/web/js/wasm:
+	$(call BUILD,$@,web)
+
 .PHONY: lint
 lint:
 	cargo fmt --check

packages/wasm-mps/package.json

@@ -11,7 +11,8 @@
   "files": [
     "dist/esm/js/**/*",
     "dist/cjs/js/**/*",
-    "dist/cjs/package.json"
+    "dist/cjs/package.json",
+    "dist/web/js/**/*"
   ],
   "exports": {
     ".": {
@@ -23,6 +24,10 @@
         "types": "./dist/cjs/js/index.d.ts",
         "default": "./dist/cjs/js/index.js"
       }
+    },
+    "./web": {
+      "types": "./dist/web/js/wasm/wasm_mps.d.ts",
+      "default": "./dist/web/js/wasm/wasm_mps.js"
     }
   },
   "main": "./dist/cjs/js/index.js",
@@ -35,7 +40,7 @@
   "scripts": {
     "test": "npm run test:mocha",
     "test:mocha": "mocha --recursive test",
-    "build:wasm": "make js/wasm && make dist/esm/js/wasm && make dist/cjs/js/wasm",
+    "build:wasm": "make js/wasm && make dist/esm/js/wasm && make dist/cjs/js/wasm && make dist/web/js/wasm",
     "build:ts-esm": "tsc",
     "build:ts-cjs": "tsc --project tsconfig.cjs.json",
     "build:ts": "npm run build:ts-esm && npm run build:ts-cjs",