metaagent session-005: METASTATE + HANDOFF

- All 7 tasks archived (T1-T7 in .agent/archive/tasks/)
- All 7 requests approved and moved to .agent/archive/requests/
- .agent/archive/index.json created
- .agent/context/project-state.md updated (post-refactor snapshot)
- .agent/handoff-summary.md (full summary for next agent)
- .agent/session-summary.md (phase-level summary)
- .agent/roadmap/sources.md (updated priorities)
- .agent/checkpoints.json: handoff=completed

All 8 phases completed: INIT, ANALYSE, ROADMAP, DECOMPOSITION,
EXECUTION, METASTATE, HANDOFF (DESIGN skipped for existing project).

.agent/archive/tasks/T3.json

@@ -0,0 +1,10 @@
+{
+  "id": "T3",
+  "title": "Decimal для денег",
+  "status": "archived",
+  "origin": "user:direct",
+  "request": "req-T3",
+  "commit": "363d440",
+  "summary": "Все денежные поля (Account.balance, Asset.value, Transaction.amount, ExchangeRate.rate, и т.д.) переведены с float на Decimal. CurrencyConverter использует Decimal арифметику с ROUND_HALF_UP. ForecastService и ScenarioService переписаны. assistant.py получил _DecimalEncoder для json.dumps. 63/63 тестов проходят.",
+  "archived_at": "2026-10-08T17:05:00Z"
+}