fix: floor malformed allowedSites, fraudContracts and selectedToken entries (closes #362)

A stored allowedSites whose value was not a list rendered a working popup and then made every subsequent save fail silently, so the user operated a wallet that persisted nothing -- worse than a blank popup, which is at least visibly broken. fraudContracts and selectedToken had the same shape: a container floored by truthiness or not at all, while its entries were dereferenced. Entries are now floored as well as containers, following the idiom #311 established, and a failed save raises a persistent banner instead of vanishing into a swallowed rejection.

The per-field justifications that used to live in a hand-written header are replaced by a contract test that drives each field's hostile and falsy values through a real popup boot, so a claim about a field answers to the code rather than to prose. Its guarantee is stated narrowly and deliberately: no structural dereference on the code paths a wholly-corrupted profile takes, which is not every path a stored record takes. The paths it does not drive are named where the claim is made, and are tracked in #379.

src/popup/index.js

@@ -1,9 +1,14 @@
 // AutistMask popup entry point.
 // Loads state, initializes views, triggers first render.
 
-const { state, saveState, loadState } = require("../shared/state");
+const {
+    state,
+    saveState,
+    onSaveFailure,
+    loadState,
+} = require("../shared/state");
 const { StateUnusableError } = require("../shared/stateSchema");
-const { setRuntimeDebug } = require("../shared/log");
+const { log, setRuntimeDebug } = require("../shared/log");
 const { refreshPrices } = require("../shared/prices");
 const { refreshBalances } = require("../shared/balances");
 const {
@@ -11,6 +16,7 @@ const {
     showView,
     updateDebugBanner,
     setBackRenderer,
+    showSaveFailureBanner,
     pushCurrentView,
     goBack,
 } = require("./views/helpers");
@@ -61,6 +67,14 @@ async function doRefreshAndRender() {
         state.lastBalanceRefresh = Date.now();
         await saveState();
         renderWalletList();
+    } catch (e) {
+        // Every call site fires this and walks away — the boot below, the ten
+        // second interval, and eight views through ctx — so it must never
+        // reject: an unhandled rejection is not a report of anything. The save
+        // inside it reports its own failure through onSaveFailure() (see
+        // src/shared/state.js); what is left here is a failed network round
+        // trip, which the next tick retries.
+        log.errorf("popup: background refresh failed:", e);
     } finally {
         refreshInFlight = false;
     }
@@ -136,6 +150,12 @@ function fallbackView() {
 }
 
 async function init() {
+    // First, before anything can save: showView() saves on every navigation
+    // without awaiting, so a save that fails from here on has somewhere to be
+    // reported rather than being swallowed by the save queue
+    // (https://git.eeqj.de/sneak/AutistMask/issues/362). Registered ahead of
+    // the approval-window branch below too, since that window saves as well.
+    onSaveFailure(showSaveFailureBanner);
     try {
         await loadState();
     } catch (e) {