harden: stop the background reading the shared state singleton, and enforce it at build time (closes #324)

Five defects, one of which destroyed every wallet, came from src/background reading and writing the module-level state singleton the MV3 worker never populates, which silently served DEFAULT_STATE. Each point fix created the next defect. The background now has its own per-call getState() and a queued read-modify-write updateState(); the singleton is unreachable from it, and an unpopulated read throws instead of serving defaults.

The prohibition is enforced by the build, not by review: build.js asserts over esbuild's own metafile that no forbidden module is an input of a background bundle, so every specifier syntax esbuild resolves is covered, and both halves of the table are checked for rot -- a stale key, a stale module, an empty list, or an unlisted entry point under src/background/ all fail the build. The ESLint rule remains as fast local feedback and reads the same shared table. Known bounds are documented where the table lives.

Also closes #320: getProvider() now requires a validated network id, so a cold worker no longer prepares a non-mainnet dApp transaction for mainnet and gets refused by the wallet's own verifier. backgroundRefresh() no longer mutates address objects across a network round trip, the broadcast path takes its endpoint and chain id from one snapshot, and eight test storage stubs now structured-clone on get as the real chrome.storage.local does.

closes #320

tests/deleteWalletLostPassword.test.js

@@ -13,13 +13,15 @@
 // never persisting it looks identical from `state`, and a build that never
 // wrote at all would pass a check that only reads `state` back.
 //
-// That makes the storage stub load-bearing, so it is a real store that
-// structured-clones on both `set` and `get`. A stub whose `get` hands back
-// the same object its `set` was given aliases the caller's own array: the
-// test then reads its own in-memory mutation and calls it persistence, and
-// passes against a build that persists nothing (see issue #324). The
-// aliasing is closed off explicitly by the first test below rather than
-// left as an assumption about `structuredClone`.
+// That makes the storage stub load-bearing, so it is the shared one from
+// tests/support/storageStub.js, a real store that structured-clones on both
+// `set` and `get`. A stub whose `get` hands back the same object its `set`
+// was given aliases the caller's own array: the test then reads its own
+// in-memory mutation and calls it persistence, and passes against a build
+// that persists nothing
+// (https://git.eeqj.de/sneak/AutistMask/issues/324). The aliasing is closed
+// off explicitly by the first test below rather than left as an assumption
+// about `structuredClone`.
 //
 // The view is driven against a minimal DOM stub, in the same shape as
 // tests/exportPrivkey.test.js: the module reads and writes named nodes and
@@ -34,6 +36,7 @@ jest.mock("../src/shared/vault", () => ({
 }));
 
 const { RESTORABLE_VIEWS } = require("../src/popup/restorableViews");
+const { makeStorageStub } = require("./support/storageStub");
 
 const VIEW = "delete-wallet-lost-password";
 
@@ -94,35 +97,6 @@ function makeDocument() {
     };
 }
 
-// --------------------------------------------------------- storage stub
-
-// A store that behaves the way `chrome.storage.local` does: what goes in is
-// serialized, so the caller keeps no handle on what came to rest there, and
-// what comes out is a fresh object the caller may mutate freely.
-function makeStorage() {
-    let store = {};
-    return {
-        get: async (keys) => {
-            const wanted =
-                keys === undefined || keys === null
-                    ? Object.keys(store)
-                    : [].concat(keys);
-            const out = {};
-            for (const key of wanted) {
-                if (key in store) out[key] = structuredClone(store[key]);
-            }
-            return out;
-        },
-        set: async (items) => {
-            for (const [key, value] of Object.entries(items)) {
-                store[key] = structuredClone(value);
-            }
-        },
-        // Test-only: what the extension would find on a cold start.
-        _raw: () => structuredClone(store),
-    };
-}
-
 // ------------------------------------------------------------ harness
 
 function wallet(name, secret, addresses) {
@@ -144,10 +118,10 @@ function load() {
     jest.resetModules();
     mockSettingsShow.mockClear();
 
-    const storage = makeStorage();
+    const storage = makeStorageStub();
     const sent = [];
     globalThis.chrome = {
-        storage: { local: storage },
+        storage: { local: storage.local },
         runtime: { sendMessage: (msg) => sent.push(msg) },
     };
     globalThis.document = makeDocument();
@@ -205,7 +179,7 @@ async function openLostPassword(deleteWallet, walletIdx) {
 // every other test in this file against a build that never writes.
 describe("the storage stub", () => {
     test("does not hand back the object it was given", async () => {
-        const storage = makeStorage();
+        const storage = makeStorageStub();
         const written = { wallets: [{ name: "Wallet 1" }] };
 
         await storage.set({ autistmask: written });
@@ -393,8 +367,8 @@ describe("deleting without the password", () => {
 
         // The deleted wallet's secret is gone from storage entirely, not
         // merely unreferenced by the wallet list.
-        expect(JSON.stringify(storage._raw())).not.toContain("secret-two");
-        expect(JSON.stringify(storage._raw())).not.toContain("xpub-Wallet 2");
+        expect(JSON.stringify(storage.read())).not.toContain("secret-two");
+        expect(JSON.stringify(storage.read())).not.toContain("xpub-Wallet 2");
     });
 
     test("only the deleted wallet's site permissions are dropped", async () => {
@@ -462,7 +436,7 @@ describe("deleting without the password", () => {
         expect(saved.activeAddress).toBeNull();
         expect(saved.allowedSites).toEqual({});
         expect(state.currentView).toBe("welcome");
-        expect(JSON.stringify(storage._raw())).not.toContain("secret-one");
+        expect(JSON.stringify(storage.read())).not.toContain("secret-one");
     });
 });