Initial scaffold: tooling, plan, task briefs

- pnpm 10 workspace + TypeScript strict + ESLint flat + Prettier
- CLAUDE.md as canonical brief
- docs/tasks/ — 22 task briefs broken out by phase for sub-sessions
- docs/decisions/ — ADR scaffold

Implements task 01 (repo-init).

docs/tasks/22-activity-log.md

@@ -0,0 +1,26 @@
+# 22 — Activity log
+
+## Goal
+
+Generic activity feed every module writes to and the dashboard reads from.
+
+## Depends on
+
+- 10, 11, 12
+
+## Scope
+
+- Schema: `activity_log` (`id`, `household_id`, `entity_type`, `entity_id`, `actor_id`, `action`, `payload` jsonb, `created_at`). Index on `(household_id, created_at desc)`.
+- `_core` exports `logActivity({ entityType, entityId, action, payload })`. Reads `householdId` and `actorId` from current session.
+- Calendar/lists/notes modules call it on create/update/delete.
+- Dashboard widget `core.activity` shows last 20 entries with human-readable rendering. Each entity type's manifest provides a `renderActivity(entry)` function.
+
+## Out of scope
+
+- Per-user activity filters.
+- Retention / pruning (no growth concerns at two-user scale).
+
+## Acceptance criteria
+
+- [ ] Every CRUD across the three core modules writes a row.
+- [ ] Widget renders entries via the registry — no `if (entityType === ...)` branches in the widget itself.