fix: a shared ticker no longer hides one of its two real tokens (closes #276)

Seven bundled tokens were filtered as spoofs at their own address, so a user
holding FRAX, TON, REUSD, EURE, MSUSD, MUSD or JPYC could not see or spend the
one the wallet happened not to pick.

The known-symbol table is derived from the bundled token list, first-wins in
market-cap order, so a symbol that appears twice silently condemned its second
contract. Both are real tokens from the same fetch and neither is stale --
three pairs are one issuer's old and new contract, four are unrelated issuers
sharing a ticker. Picking a winner would have been guessing, and dropping the
ambiguous symbols would have ended spoof filtering for those tickers entirely.

The table now maps a symbol to the set of addresses that legitimately bear it.
A contract outside the set is still a spoof, so the check is not weakened: a
third contract bearing any of the seven shared tickers is refused, and that is
tested. The filter decides what is fake, not what is worth holding, so a legacy
contract stays in the set -- it still holds real balances.

A test walks the whole bundled list asserting no token is filtered at its own
address, which is the guard whose absence let this ship.

src/shared/symbolSpoof.js

@@ -8,12 +8,19 @@
 // either verdict alone, because the balance list is where the user forms
 // their belief about what they own (issue #235).
 //
-// KNOWN_SYMBOLS maps a symbol to the lowercased contract address that may
-// bear it, or to null.  Null means the symbol belongs to the native asset,
-// which has no contract at all, so no contract may bear it and every one
-// that does is a spoof.  "ETH" is the only such entry today; the rule is
+// KNOWN_SYMBOLS maps a symbol to the set of lowercased contract addresses
+// that may bear it, or to null.  Null means the symbol belongs to the native
+// asset, which has no contract at all, so no contract may bear it and every
+// one that does is a spoof.  "ETH" is the only such entry today; the rule is
 // written so that a second one needs no change here or at any call site.
 //
+// The value is a set because a ticker is not unique: seven symbols in the
+// bundled list belong to two real contracts each, and answering with one of
+// them hid the other one's holders' money (issue #276).  Membership, not
+// equality, is therefore the question — but it is the same question, asked of
+// a table that can now state the truth.  Every address in a set is one the
+// wallet ships as a real token; a contract outside the set is still a spoof.
+//
 // The symbol is attacker-controlled — it is whatever the ERC-20 contract
 // returns — so the lookup is done on a normalized form (issue #260): the
 // question is whether the symbol reaches the user's eye as a known one,
@@ -93,7 +100,7 @@ function isSpoofedSymbol(symbol, contractAddress) {
     if (!KNOWN_SYMBOLS.has(sym)) return false;
     const legit = KNOWN_SYMBOLS.get(sym);
     if (legit === null) return true;
-    return contract !== normalizeAddress(legit);
+    return !legit.has(contract);
 }
 
 module.exports = {