Merge RB-20 — route cancel and delete through runSubmit, surface the error

CQ-002: ApplicationsStore.cancel and AdminCasesStore.delete reached the raw
ApiClient and swallowed the failure in a bare catch, so a failed cancel made the
row reappear with no message. Both now fold through runSubmit and expose
lastError, which the two pages render.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

# Conflicts:
#	docs/project/refactor-backlog-setup/refactor-backlog/99-backlog.md
#	libs/shared/docs/behaviour-spec.mdx

libs/shared/docs/behaviour-spec.mdx

@@ -20,7 +20,7 @@ tested where._
 
 Every bullet below is a real test name from the suite — an `it()` title (frontend) or a test
 method name (backend), read as a sentence. Nothing here is hand-written prose: this page
-**is** the suite, reshaped for a business reader. 460 frontend behaviours across
+**is** the suite, reshaped for a business reader. 465 frontend behaviours across
 9 contexts; 237 backend behaviours across 41 test
 classes.
 
@@ -406,7 +406,15 @@ classes.
 
 - loads and parses the cross-owner list
 - deletes optimistically and confirms via the admin endpoint
-- rolls back the removal when the delete fails
+- rolls back the removal and surfaces the error when the delete fails
+- clears a stale error on the next delete attempt
+
+#### ApplicationsStore
+
+- loads and parses the list
+- cancels optimistically and confirms via the DELETE endpoint
+- rolls back the removal and surfaces the error when the cancel fails
+- clears a stale error on the next cancel attempt
 
 #### STEPS (fixed)