fix: keep every flash message on the one line it reserves (closes #252)

The flash line reserves one line of height, so a message that wrapped
pushed the screen below it down. Every message is now at most 50
characters, one line of the popup's monospace font: the longer ones are
reworded, and the ones that carried a wallet name or text from a server
no longer do. The rule is written at showFlash().

A new end-to-end test drives the longest message and fails if the
line's rendered height grows. It measures in the monospace font, which
Firefox draws and Chromium does not.

Model: opus-5-5

TODO.md

@@ -45,6 +45,20 @@ but the review is broader than any of them.
 
 # Completed Steps
 
+- 2026-10-04: Every flash message fits on the one line the flash line reserves,
+  and a test measures it
+  ([#252](https://git.eeqj.de/sneak/AutistMask/issues/252)). A message that
+  wrapped pushed the whole screen below it down. Rather than reserve a second
+  line on every screen or let the flash cover the screen, every message is now
+  at most 50 characters, one line of the popup's monospace font: the longer ones
+  are reworded, and messages that carried a wallet name or text from a server no
+  longer do, since neither has a length limit. The rule is written at
+  `showFlash()` in `src/popup/views/helpers.js`. A new test in
+  `tests/e2e/run.js` drives the longest message and fails if the line's rendered
+  height grows. It measures in the monospace font, because Chromium draws the
+  popup in its narrower system font and only Firefox shows the wrap. The two
+  approval-screen error boxes are left to
+  [#297](https://git.eeqj.de/sneak/AutistMask/issues/297).
 - 2026-10-04: Removing an address or deleting a wallet ends every site
   connection approved without "Remember" for the addresses removed
   ([#245](https://git.eeqj.de/sneak/AutistMask/issues/245)). Such a connection