test: drive WaitTx's timeout and failed-lookup exits end to end (closes #315)

Two Chrome end-to-end cases send ETH and leave the wait for its receipt
running. In one, lookups answer "no receipt" until the 60-second deadline
ends the wait with the timeout message. In the other, a new fixture switch
makes every receipt lookup fail, and the sixth failure in a row ends the
wait with the message naming the unreachable network. Both check the exact
message and that Done returns to the address screen. Both wait in real
time: Playwright's clock would apply to every later test, and backdating
the stored broadcast time races the popup's own save.

Model: opus-5-5

README.md

@@ -376,6 +376,12 @@ reserve while sitting on the same side of the estimate, so swapping the two in
 what [#154](https://git.eeqj.de/sneak/AutistMask/issues/154) was, and it was
 previously correct by reading only.
 
+It also covers both ways the wait for a sent transaction's receipt ends on the
+error screen: lookups that still find no receipt 60 seconds after the broadcast,
+and six lookups in a row that fail. Each must show its own message, and Done
+must lead back to the address screen. Both wait in real time, about a minute
+each.
+
 It also covers the **dApp approval round trips** — the one place where the
 content script, the inpage provider, the background worker and the approval
 popup all have to work together. A local test page is served by the route
@@ -640,7 +646,9 @@ suite outright if its network interception is not in effect.
 Measured on this repo's runner: `e2e-chrome` about 1m55s cold, almost all of it
 the one-time pull of the pinned ~800MB Playwright layer, and well under a minute
 once that layer is cached. `e2e-firefox` about 1m05s cold, and it caches its
-Firefox and geckodriver downloads the same way.
+Firefox and geckodriver downloads the same way. The `e2e-chrome` figures predate
+the two cases that wait for a receipt to end in error, which add about two
+minutes of real waiting.
 
 ### Element id guard (part of `make check`)