feat(orchestrator): DataGate 机制化 + 任务级持久化（T14/T16 架构审查整改）

- T14 (OV5): 新建 src/genesis/orchestrator/datagate.py
  - DataGate.load(source, selector) 机制化：子集加载 + 规模保护（超 500 行
    无 selector 拒绝全量，1000 行 Excel 防上下文爆炸）+ token 预算（8000，
    复用 CJK 保守估算）+ 未知表容错
  - agent-runtime §4.2 原则→机制说明
- T16 (OV7): 新建 src/genesis/orchestrator/task_queue.py
  - TaskQueue ABC + PersistentTaskQueue（SQLite 落盘）
  - enqueue/poll/update_status/get/cancel/recover/close
  - 幂等去重（§5.3 缓存结果）+ recover 将 running→failed、pending 保留
  - api-design §5.2/5.3、agent-runtime §3.5/3.6、design §8.4.1 同步
- 新增 test_datagate.py（8 用例）+ test_task_queue.py（11 用例）
- TDD: RED（模块缺失）→ GREEN（聚焦 16 passed）→ 全量 218 passed / 100.00%（1140 stmts/278 br）

tests/test_datagate.py

@@ -0,0 +1,137 @@
+"""DataGate 机制化测试（T14，OV5）。
+
+OV5 裁定：DataGate 是原则非机制，1000 行 Excel 上下文爆炸
+→ 机制化：规模保护（超阈值无 selector 拒绝全量）+ token 预算控制 + 子集加载。
+"""
+
+from __future__ import annotations
+
+import pytest
+
+from genesis.data_models import CellValue, ExcelTable, Provenance, SheetType
+from genesis.orchestrator.datagate import (
+    DataGate,
+    DataGateError,
+    DataSelector,
+    DataGateResult,
+)
+
+
+def _table(name: str, n_rows: int) -> ExcelTable:
+    rows: list[dict[str, CellValue]] = []
+    for i in range(n_rows):
+        rows.append({
+            "ID": CellValue(
+                value=f"{name}-{i}",
+                provenance=Provenance(file_name="要件定義.xlsx", sheet_name=name, row=i + 2, column="A", column_header="ID"),
+            )
+        })
+    return ExcelTable(
+        name=name,
+        detected_type=SheetType.FUNCTION,
+        extraction_method="structured",
+        headers=["ID"],
+        rows=rows,
+    )
+
+
+# ---------- 子集加载 ----------
+
+def test_load_returns_selector_subset():
+    gate = DataGate()
+    source = _source_with_tables(["機能一覧", "画面一覧"], rows_each=5)
+
+    result = gate.load(source, DataSelector(table_ids=["画面一覧"]))
+
+    assert isinstance(result, DataGateResult)
+    assert result.loaded_tables == ["画面一覧"]
+    assert result.loaded_rows == 5
+
+
+# ---------- 规模保护（OV5 核心：1000 行 Excel 防上下文爆炸） ----------
+
+def test_load_rejects_huge_source_without_selector():
+    gate = DataGate(max_total_rows=500)
+    source = _source_with_tables(["機能一覧"], rows_each=1000)
+
+    with pytest.raises(DataGateError, match="selector"):
+        gate.load(source)
+
+
+def test_load_allows_small_source_without_selector():
+    gate = DataGate(max_total_rows=500)
+    source = _source_with_tables(["機能一覧"], rows_each=10)
+
+    result = gate.load(source)
+
+    assert result.loaded_rows == 10
+
+
+def test_huge_source_with_selector_is_allowed():
+    """1000 行 Excel + selector 限定单表 → 不触发全量防护。"""
+    gate = DataGate(max_total_rows=500)
+    source = _source_with_tables(["機能一覧", "画面一覧", "帳票一覧"], rows_each=1000)
+
+    result = gate.load(source, DataSelector(table_ids=["画面一覧"]))
+
+    assert result.loaded_tables == ["画面一覧"]
+    assert result.loaded_rows == 1000
+
+
+# ---------- token 预算控制 ----------
+
+def test_token_budget_rejects_huge_load():
+    gate = DataGate(max_total_tokens=100)
+    source = _source_with_tables(["機能一覧"], rows_each=200)
+
+    with pytest.raises(DataGateError, match="token"):
+        gate.load(source, DataSelector(table_ids=["機能一覧"]))
+
+
+def test_token_budget_ok_within_limit():
+    gate = DataGate(max_total_tokens=10_000)
+    source = _source_with_tables(["機能一覧"], rows_each=20)
+
+    result = gate.load(source, DataSelector(table_ids=["機能一覧"]))
+
+    assert result.token_estimate <= 10_000
+
+
+# ---------- 未知表容错 ----------
+
+def test_unknown_table_id_returns_empty():
+    gate = DataGate()
+    source = _source_with_tables(["機能一覧"], rows_each=5)
+
+    result = gate.load(source, DataSelector(table_ids=["不存在"]))
+
+    assert result.loaded_tables == []
+    assert result.loaded_rows == 0
+
+
+def test_empty_selector_equals_no_selector():
+    """selector 未指定任何表 → 等同无 selector，触发规模保护。"""
+    gate = DataGate(max_total_rows=10)
+    source = _source_with_tables(["機能一覧"], rows_each=100)
+
+    with pytest.raises(DataGateError, match="selector"):
+        gate.load(source, DataSelector())
+
+
+def _source_with_tables(names: list[str], rows_each: int):
+    from genesis.data_models import (
+        ExistingSystemInfo,
+        ImageAnalysis,
+        ParsedTemplate,
+        RuleDocument,
+        StructuredSource,
+    )
+
+    return StructuredSource(
+        tables=[_table(n, rows_each) for n in names],
+        template=ParsedTemplate(file_name="template.docx", sections=[], placeholders={}, styles={}),
+        rule_docs=[],
+        image_analyses=[],
+        existing_system=None,
+        comments=[],
+    )