fix: discard-dist-on-failure keeps the step's status when its message cannot be written (closes #342)

With stderr closed, the wrapper's message write failed and set -e ended it
with status 2; with stderr a pipe whose reader had gone, the write killed it
with 141. The message is now written with SIGPIPE ignored and its failure
ignored, after the step has run. An interrupt while a step runs now exits with
130 once the step has ended, removing nothing: under bash, a step that caught
the interrupt and exited with a status, as check-censored does, used to get
dist/ removed. A failed check-censored --require-dist still removes dist/. The
header states both. Also the README bullet's missing period.

Model: opus-5-5

TODO.md

@@ -45,6 +45,20 @@ but the review is broader than any of them.
 
 # Completed Steps
 
+- 2026-10-07: `script/discard-dist-on-failure` returns the failed step's own
+  exit status even when it cannot write its message, to a closed stderr or to a
+  pipe nobody reads any more
+  ([#342](https://git.eeqj.de/sneak/AutistMask/issues/342)); it used to return 2
+  or 141 instead. An interrupt while a step runs now removes nothing and says
+  nothing whichever shell `/bin/sh` is, even when the step catches it and exits
+  with a status of its own, as `script/check-censored` does: the wrapper exits
+  with 130 once the step has ended. Under bash such a step used to have `dist/`
+  removed. A failed `check-censored --require-dist` still removes `dist/` like
+  any other step, because a `dist/` not cleared of the name `RULES.md` bars must
+  not ship. The header states both. `script/test-verify-build` runs the wrapper
+  with stderr closed and with stderr a pipe nobody reads, and interrupts it
+  under dash and under bash.
+
 - 2026-10-06: Back from Settings no longer lands on the delete wallet or
   lost-password screen after either was left by the settings gear
   ([#480](https://git.eeqj.de/sneak/AutistMask/issues/480)), the defect