fix: tracked tokens are kept per network, and bundled picks are offered on mainnet only (closes #523)

A network switch now puts the outgoing network's tracked tokens away in a new
persisted field, networkTrackedTokens, and brings back the incoming network's
list, or an empty one, the way endpoints are already kept per network.
trackedTokens stays the active network's list, so its readers are unchanged,
and the background's switch keeps the lists too because it goes through the
same function. The two add-token screens show their common-token picks, which
come from the bundled list of mainnet contracts, on Ethereum Mainnet only;
adding by contract address works on every network. Settings redraws its
tracked-token list after a switch.

Model: opus-5-5

src/shared/chainSwitchFields.js

@@ -38,6 +38,16 @@ function applyChainSwitchFields(s, newNetworkId) {
         blockscoutUrl: s.blockscoutUrl,
     };
     const remembered = s.networkEndpoints[net.id] || {};
+
+    // Tracked tokens are kept per network the same way, because a contract
+    // address names a token on one network only. s.trackedTokens stays the
+    // active network's list, so nothing that reads it changes: the outgoing
+    // list is put away under its network, and the incoming network's list, or
+    // an empty one, takes its place.
+    if (!s.networkTrackedTokens) s.networkTrackedTokens = {};
+    s.networkTrackedTokens[s.networkId] = s.trackedTokens;
+    s.trackedTokens = s.networkTrackedTokens[net.id] || [];
+
     s.networkId = net.id;
     s.rpcUrl = remembered.rpcUrl || net.defaultRpcUrl;
     s.blockscoutUrl = remembered.blockscoutUrl || net.defaultBlockscoutUrl;

src/shared/persistedState.js

@@ -23,6 +23,11 @@ const DEFAULT_STATE = {
     hasWallet: false,
     wallets: [],
     trackedTokens: [],
+    // Tracked tokens remembered per network: { [networkId]: [token, ...] }.
+    // trackedTokens above is the active network's list; this is what the
+    // others are restored from when the active network changes. See
+    // applyChainSwitchFields().
+    networkTrackedTokens: {},
     networkId: "mainnet",
     rpcUrl: DEFAULT_RPC_URL,
     blockscoutUrl: DEFAULT_BLOCKSCOUT_URL,
@@ -289,6 +294,20 @@ function normalizePersisted(saved) {
     // profile whose wallets are perfectly fine. An empty list is a legitimate
     // value and survives.
     out.trackedTokens = structuredClone(tokenRefs(saved.trackedTokens));
+    // Each remembered list is floored like trackedTokens, because
+    // applyChainSwitchFields() puts it straight back onto trackedTokens when
+    // its network becomes the active one. A key that is not a network in
+    // networks.js is dropped, which also keeps an own "__proto__" key from
+    // reaching the plain assignment below.
+    out.networkTrackedTokens = {};
+    if (isRecord(saved.networkTrackedTokens)) {
+        for (const netId of Object.keys(saved.networkTrackedTokens)) {
+            if (!isKnownNetworkId(netId)) continue;
+            out.networkTrackedTokens[netId] = structuredClone(
+                tokenRefs(saved.networkTrackedTokens[netId]),
+            );
+        }
+    }
     // The loud refusal for an unknown id is assertStateUsable(); this is the
     // floor under it. networkId is an object KEY into networkEndpoints below,
     // so a value that is not a network in networks.js must never get that far

src/shared/state.js

@@ -42,9 +42,11 @@ const { log } = require("./log");
 // and writes THIS object, never the proxy: the guard is for callers.
 const rawState = {
     ...DEFAULT_STATE,
-    // Its own object, not the one DEFAULT_STATE holds: applyChainSwitchFields()
-    // mutates this map in place, and a spread copies the reference.
+    // Their own objects, not the ones DEFAULT_STATE holds:
+    // applyChainSwitchFields() mutates these maps in place, and a spread copies
+    // the reference.
     networkEndpoints: {},
+    networkTrackedTokens: {},
     currentView: null,
     selectedWallet: null,
     selectedAddress: null,
@@ -438,12 +440,14 @@ function mergeNetworkEndpoints(base, ours, theirs) {
 //
 // Every other persisted field stays a whole-field diff:
 // `trackedTokens`/`fraudContracts`/`viewStack` are arrays of scalars with no
-// per-element identity to merge by; `tokenHolderCache` is a map shaped like
-// the ones above, but nothing in src/ ever writes an entry into it — it is
-// only ever reset wholesale to `{}` (applyChainSwitchFields()) — so there is
-// no in-place mutation for a whole-field diff to collide with; `viewData` is
-// this page's own UI scratch space, not data another page has any reason to
-// share membership of.
+// per-element identity to merge by; `networkTrackedTokens` is diffed whole like
+// `trackedTokens` and `networkId`, the two fields a network switch moves
+// together with it; `tokenHolderCache` is a map shaped like the ones above,
+// but nothing in src/ ever writes an entry into it — it is only ever reset
+// wholesale to `{}` (applyChainSwitchFields()) — so there is no in-place
+// mutation for a whole-field diff to collide with; `viewData` is this page's
+// own UI scratch space, not data another page has any reason to share
+// membership of.
 //
 // This does not make two pages that both change the SAME leaf concurrently
 // safe: last write wins on that one leaf, same as before. What it removes