fix: keep the flash line to its one line at any message length (closes #252)

The flash line reserves one line, so a message that wrapped pushed the
screen below it down. #flash-msg no longer wraps: text too long for it is
cut with an ellipsis, and showFlash() puts the whole message in its title.
Every message is also reworded to at most 50 characters so none is cut,
and the add-token screens flash a fixed line for any error other than the
two lookup messages, logging the detail.

A new end-to-end test writes a message several lines long into the line
and fails if the line or the screen below it moves.

Model: opus-5-5

TODO.md

@@ -56,14 +56,6 @@ but the review is broader than any of them.
   message several lines long on the line and fails if the line or the screen
   below it moves. The two approval-screen error boxes are left to
   [#297](https://git.eeqj.de/sneak/AutistMask/issues/297).
-
-- 2026-10-04: A method the wallet does not implement is refused with EIP-1193
-  code `4200` ([#279](https://git.eeqj.de/sneak/AutistMask/issues/279)). The
-  background's `Unsupported method: <method>` error carried no code, so a site
-  probing for an optional method could not tell "not implemented" from "the call
-  failed". The message is unchanged; the background's other errors with no code
-  are untouched.
-
 - 2026-10-04: Settings lists the sites connected without "Remember", and
   removing a site there disconnects it
   ([#406](https://git.eeqj.de/sneak/AutistMask/issues/406)). Such a connection

src/background/index.js

@@ -932,9 +932,7 @@ async function handleRpc(method, params, origin) {
         }
     }
 
-    // EIP-1193 4200 lets a site tell "this wallet does not implement that"
+    return { error: { message: "Unsupported method: " + method } };
-    // from "that call failed", and fall back.
-    return { error: { code: 4200, message: "Unsupported method: " + method } };
 }
 
 // The body of eth_sendTransaction, from the connection check through to the

src/content/inpage.js

@@ -31,12 +31,11 @@
     // an error instead of accepting the refusal.
     //
     // Whatever code arrived is passed through verbatim rather than being
-    // matched against a list: the extension emits codes such as 4001, 4100,
+    // matched against a list: the extension emits 4001, 4100 and 4902 today,
-    // 4200 and 4902, and a code this file has never heard of is still the
+    // and a code this file has never heard of is still the truth about what
-    // truth about what happened. An error reported with no code at all stays
+    // happened. An error reported with no code at all stays a plain Error —
-    // a plain Error — a ProviderRpcError whose `code` is undefined would
+    // a ProviderRpcError whose `code` is undefined would advertise a
-    // advertise a conformance it does not have. `message` is untouched in
+    // conformance it does not have. `message` is untouched in every case.
-    // every case.
     function toPageError(error) {
         const message = (error && error.message) || "Request failed";
         if (error && error.code !== undefined && error.code !== null) {

tests/inpageErrors.test.js

@@ -49,12 +49,11 @@ class StubCustomEvent extends StubEvent {
     }
 }
 
-// Examples of codes the background emits on the RPC path, read out of
+// Every code the background emits on the RPC path today, read out of
-// src/background/index.js. The provider must not know any list of codes — it
+// src/background/index.js. The provider must not know this list — it passes
-// passes through whatever arrived — but the cases below are real ones.
+// through whatever arrived — but the cases below are the real ones.
 const REJECTED = 4001; // user rejected the request
 const UNAUTHORIZED = 4100; // site not connected / wrong address
-const UNSUPPORTED_METHOD = 4200; // a method the wallet does not implement
 const UNRECOGNIZED_CHAIN = 4902; // switch/add to an unsupported chain
 
 // A stub window with the four things inpage.js touches: message listeners,
@@ -116,41 +115,6 @@ async function rejectionFrom(start, response) {
     return outcome.error;
 }
 
-// The reply the real background worker (src/background/index.js) sends for
-// `method`, loaded against just enough of the extension API to receive one
-// RPC message. Same shape as tests/coldWorkerChainId.test.js.
-function backgroundReply(method) {
-    jest.resetModules();
-    jest.doMock("../src/shared/alarms", () => ({
-        BALANCE_REFRESH_ALARM: "balance",
-        BALANCE_REFRESH_PERIOD_MINUTES: 1,
-        ensureRecurringAlarms: async () => {},
-        registerAlarmHandlers: () => {},
-    }));
-
-    let messageListener = null;
-    global.chrome = {
-        runtime: {
-            onMessage: {
-                addListener: (fn) => {
-                    messageListener = fn;
-                },
-            },
-            onConnect: { addListener: () => {} },
-        },
-    };
-
-    require("../src/background/index");
-
-    return new Promise((resolve) => {
-        messageListener(
-            { type: "AUTISTMASK_RPC", method, params: [] },
-            { origin: "https://dapp.example" },
-            resolve,
-        );
-    });
-}
-
 describe("an EIP-1193 code reaches the page", () => {
     test("a user rejection arrives as code 4001", async () => {
         const err = await rejectionFrom(
@@ -200,9 +164,8 @@ describe("an EIP-1193 code reaches the page", () => {
         expect(err.message).toBe(message);
     });
 
-    // The provider is not allowed to know the codes above: any other code,
+    // The provider is not allowed to know the list above: a code added to the
-    // including one added to the background later, must reach the page
+    // background later must reach the page without this file being edited.
-    // without inpage.js being edited.
     test("a code the provider has never heard of is passed through", async () => {
         const err = await rejectionFrom(
             (p) => p.request({ method: "eth_accounts" }),
@@ -240,26 +203,6 @@ describe("an EIP-1193 code reaches the page", () => {
     });
 });
 
-// The reply here is the background's own, not one written in this file: it
-// used to carry no code for a method the wallet does not implement
-// (https://git.eeqj.de/sneak/AutistMask/issues/279), so a site probing for an
-// optional method could not tell "not implemented" from "the call failed".
-describe("a method the wallet does not implement", () => {
-    afterEach(() => {
-        delete global.chrome;
-    });
-
-    test("reaches the page as code 4200", async () => {
-        const method = "wallet_noSuchMethod";
-        const err = await rejectionFrom(
-            (p) => p.request({ method }),
-            await backgroundReply(method),
-        );
-        expect(err.code).toBe(UNSUPPORTED_METHOD);
-        expect(err.message).toBe("Unsupported method: " + method);
-    });
-});
-
 describe("the message is untouched", () => {
     test("a coded error keeps the message byte for byte", async () => {
         const message =