docs(sdd): append hotfix summary for applyMutation and list keys

.superpowers/sdd/task-4-report.md

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+# Task 4 Report — StepDbSettings Rewrite
+
+## Status: DONE_WITH_CONCERNS
+
+## Commit: d309faf
+
+## TSC Summary
+Zero new errors introduced in `step-db-settings.tsx`. All pre-existing errors in the repo are unrelated (in `form.tsx`, `toaster.tsx`, `channel-form.tsx`, `database-form.action.ts`, etc.).
+
+## What Was Done
+Replaced the placeholder implementation of `StepDbSettings` (~91 lines, only retention days + apply-to-all switch) with the full three-level phase navigation component (~1050 lines):
+
+- **Phase: grid** — lists all project databases with "Configured" badge when any section is set
+- **Phase: db** — shows 4 section cards (Retention, Scheduling, Notifications, Storage) with per-section ✓ indicators and "Apply to all" button
+- **Phase: section** — renders the appropriate inline section form
+
+All 4 sections implemented inline (no dashboard component imports):
+- `RetentionSection`: count / days / GFS with storage impact estimate
+- `SchedulingSection`: delegates to `BackupScheduleSelector`
+- `NotificationsSection`: multi-policy, `MultiSelect` for events, empty-state when no notifiers
+- `StorageSection`: multi-policy, empty-state when no storages
+
+Save flow: calls `applyOnboardingDbSettingsAction` → on success calls `updateDbSettings(dbId, patch)` → toast → phase back to db.
+
+"Apply to all": loops over other DB IDs, calls action with `section: "all"` for each, batch-updates context, shows toast, navigates to grid.
+
+## Concerns
+1. **Type cast on `notificationPolicies`**: `OnboardingNotificationPolicy.eventKinds` is typed as `string[]` but the action's Zod schema uses a specific enum union. Two `as any` casts were added at action call sites to bridge the mismatch. The runtime is safe (Zod validates and rejects invalid values), but the type inconsistency between `types/index.ts` and `apply-db-settings.action.ts` should be resolved by tightening `OnboardingNotificationPolicy.eventKinds` to the same enum type as the action's `EventKindSchema`.
+
+2. **No browser test performed**: manual verification steps from the brief (Steps 3–5) were not executed as they require a running dev server and live DB. The component logic follows the brief exactly.
+
+---
+
+## Hotfix Follow-up Commit: a6e528d
+
+Fixed two critical issues:
+
+1. **Wire `applyMutation.mutateAsync` everywhere** (5 sites):
+   - Replaced all direct `applyOnboardingDbSettingsAction(...)` calls with `await applyMutation.mutateAsync(...)`
+   - Removed `if (result?.data?.success)` guards since mutateAsync throws on error
+   - Mutation's `onError: () => toast.error(...)` handles failures
+
+2. **Stabilize list keys**:
+   - NotificationsSection: changed `key={index}` to `key={policy.channelId || index}`
+   - StorageSection: changed `key={index}` to `key={policy.channelId || index}`
+
+TypeScript: Zero new errors in target file. Pre-existing errors in form.tsx, toaster.tsx, channel-form.tsx (unrelated).