chore: prune landed remote branches (closes #167)

Seventeen branches on origin that the issue classifies as landed, or
superseded by a merged pull request, were deleted; the evidence for each
is on the issue. Five whose work is not in next are kept: the three
issue 87 error-display branches and feature/show-private-key, reference
for issues 493 and 492, and chore/token-list-enrichment, re-created at
f7a2437, pending issue 495. TODO.md records this.

The branch-pruning Future Step had already left TODO.md in the issue 191
rewrite, so only the Completed Steps entry is added.

Model: opus-5-5

TODO.md

@@ -45,6 +45,27 @@ but the review is broader than any of them.
 
 # Completed Steps
 
+- 2026-10-07: Stale branches pruned from `origin`
+  ([#167](https://git.eeqj.de/sneak/AutistMask/issues/167)). The issue
+  classifies each branch it lists, with the evidence. The seventeen still on
+  `origin` that it classifies as landed, or superseded by a merged pull request,
+  were deleted. `feat/message-signing` and `fix/59-transaction-view-ui-policies`
+  had been deleted on 2026-09-09; both landed and stay deleted. Five are kept
+  because their work is not in `next`: `fix/consistent-error-display`,
+  `fix/87-consistent-error-display` and `fix/87-consistent-error-display-v2`,
+  the change for [#87](https://git.eeqj.de/sneak/AutistMask/issues/87) that
+  never landed, as reference for
+  [#493](https://git.eeqj.de/sneak/AutistMask/issues/493);
+  `feature/show-private-key`, whose README clipboard policy section is reference
+  for [#492](https://git.eeqj.de/sneak/AutistMask/issues/492); and
+  `chore/token-list-enrichment`, deleted on 2026-09-09 and re-created at
+  `f7a2437`, whose `scripts/` tooling waits on
+  [#495](https://git.eeqj.de/sneak/AutistMask/issues/495). Afterwards
+  `git ls-remote --heads origin` showed `main`, `next`, these five, and
+  `issue-167-prune-branches` and `issue-492-readme-clipboard`, the heads of the
+  open pull requests [#491](https://git.eeqj.de/sneak/AutistMask/pulls/491) and
+  [#494](https://git.eeqj.de/sneak/AutistMask/pulls/494).
+
 - 2026-10-07: The Firefox end-to-end suite no longer tolerates any uncaught
   extension error ([#487](https://git.eeqj.de/sneak/AutistMask/issues/487)). Its
   one entry, Firefox reporting a popup promise that settled after the page