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

@@ -45,6 +45,18 @@ but the review is broader than any of them.
 
 # Completed Steps
 
+- 2026-10-04: The flash line keeps to the one line it reserves at any message
+  length ([#252](https://git.eeqj.de/sneak/AutistMask/issues/252)). A message
+  that wrapped pushed the whole screen below it down. `#flash-msg` no longer
+  wraps: text too long for the line is cut with an ellipsis, and `showFlash()`
+  puts the whole message in the line's title. Every message is also reworded to
+  at most 50 characters so none is cut; none carries a wallet name or text from
+  a server, and the add-token screens flash a fixed line for any error other
+  than a contract that is not a token. A new test in `tests/e2e/run.js` puts a
+  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