build: remove dist/ when a release build fails (closes #333)

A failed release build no longer leaves a complete, loadable debug bundle in dist/ whose every wallet uses the publicly committed test recovery phrase. Each step of the release build runs through script/discard-dist-on-failure, which removes dist/ on failure, says on stderr that it did and why, and returns the step's own status. build-debug is deliberately unwrapped. script/verify-build is untouched.

TODO.md

@@ -45,6 +45,19 @@ but the review is broader than any of them.
 
 # Completed Steps
 
+- 2026-08-23: A failed release build no longer leaves a loadable debug bundle in
+  `dist/` ([#333](https://git.eeqj.de/sneak/AutistMask/issues/333)). With
+  `AUTISTMASK_DEBUG=1` exported, `make build` compiled a debug bundle and failed
+  on it in `script/verify-build` — but the bundle stayed on disk, loadable, with
+  every wallet it creates using the publicly committed test recovery phrase.
+  Every step of `make build` now runs through `script/discard-dist-on-failure`,
+  which removes `dist/` when a step fails and says on stderr that it did and
+  why; a removal it cannot complete is reported just as loudly.
+  `make build-debug` is deliberately not wrapped: its output is not mistakable
+  for a release build and is the evidence of the failure.
+  `script/test-verify-build` asserts the state of `dist/` on disk after a
+  failing and a succeeding step, not just the exit status, and reads `make -n`
+  to check the wrapper is on the release path and only there.
 - 2026-08-23: `README.md` and `script/verify-build`'s own comments now state the
   emitted-tree guarantee at the width the code actually enforces
   ([#331](https://git.eeqj.de/sneak/AutistMask/issues/331)). The tree walk is