test(agent): finish A-101 internal branch coverage for DareAgent split

docs/design/modules/agent/TODO.md

@@ -1,6 +1,6 @@
 # Agent TODO
 
-> 更新日期：2026-02-27
+> 更新日期：2026-03-03
 > 说明：Agent 模块唯一补齐清单（用于范围讨论与执行跟踪）
 
 ## 1. 本轮范围建议（用于你我讨论）
@@ -34,7 +34,7 @@
   - `dare_framework/agent/_internal/milestone_orchestrator.py`
   - `dare_framework/agent/_internal/execute_engine.py`
   - `dare_framework/agent/_internal/tool_executor.py`
-  - `tests/unit/test_dare_agent_orchestration_split.py`（新增委托边界测试）
+  - `tests/unit/test_dare_agent_orchestration_split.py`（委托边界测试 + `_internal` execute/tool/milestone 分支定向单测）
   - 受影响回归：`tests/unit/test_five_layer_agent.py`、`tests/unit/test_dare_agent_hook_governance.py`、`tests/unit/test_dare_agent_hook_transport_boundary.py`
 
 ### A-102 step-driven 路径闭环（P1）

docs/features/refactor-dare-agent-structure-split.md

@@ -0,0 +1,60 @@
+---
+change_ids: ["refactor-dare-agent-structure-split"]
+doc_kind: feature
+topics: ["agent", "refactor", "orchestration", "testing"]
+created: 2026-03-03
+updated: 2026-03-03
+status: active
+mode: openspec
+---
+
+# Feature: refactor-dare-agent-structure-split
+
+## Scope
+
+完成 A-101 的最后一项收尾：在 `DareAgent` façade delegation 已拆分完成的前提下，为 `_internal` 的 `execute_engine`、`tool_executor`、`milestone_orchestrator` 补齐 direct unit tests，锁住 success/failure/approval/policy/retry 分支语义。
+
+## OpenSpec Artifacts
+
+- Proposal: `openspec/changes/refactor-dare-agent-structure-split/proposal.md`
+- Design: `openspec/changes/refactor-dare-agent-structure-split/design.md`
+- Tasks: `openspec/changes/refactor-dare-agent-structure-split/tasks.md`
+
+## Governance Anchors
+
+- `docs/design/modules/agent/TODO.md`
+- `docs/design/TODO_INDEX.md`
+
+## Evidence
+
+### Commands
+
+- `git worktree add .worktrees/refactor-dare-agent-structure-split -b codex/refactor-dare-agent-structure-split origin/main`
+- `../../.venv/bin/python -m pytest -q tests/unit/test_dare_agent_orchestration_split.py tests/unit/test_five_layer_agent.py tests/unit/test_dare_agent_hook_governance.py tests/unit/test_dare_agent_hook_transport_boundary.py`
+- `../../.venv/bin/python -m pytest -q tests/unit/test_dare_agent_orchestration_split.py -k 'before_model_hook_blocks or no_tool_calls or preflight_denies or done_predicate_is_satisfied or plan_policy_failure'`
+- `../../.venv/bin/python -m pytest -q tests/unit/test_dare_agent_orchestration_split.py`
+- `../../.venv/bin/python -m pytest -q tests/unit/test_five_layer_agent.py tests/unit/test_dare_agent_hook_governance.py tests/unit/test_dare_agent_hook_transport_boundary.py`
+
+### Results
+
+- `git worktree add ... origin/main`: created an isolated continuation workspace for the final A-101 closeout from `origin/main` commit `5d1cfb4`.
+- `../../.venv/bin/python -m pytest -q tests/unit/test_dare_agent_orchestration_split.py tests/unit/test_five_layer_agent.py tests/unit/test_dare_agent_hook_governance.py tests/unit/test_dare_agent_hook_transport_boundary.py`: baseline passed (`43 passed, 1 warning`) before adding new tests, confirming the change started from a clean regression surface.
+- `../../.venv/bin/python -m pytest -q tests/unit/test_dare_agent_orchestration_split.py -k 'before_model_hook_blocks or no_tool_calls or preflight_denies or done_predicate_is_satisfied or plan_policy_failure'`: passed (`4 passed, 5 deselected, 1 warning`) after adding the new direct `_internal` branch coverage.
+- `../../.venv/bin/python -m pytest -q tests/unit/test_dare_agent_orchestration_split.py`: passed (`9 passed, 1 warning`) with both the existing façade delegation assertions and the new direct execution-unit tests.
+- `../../.venv/bin/python -m pytest -q tests/unit/test_five_layer_agent.py tests/unit/test_dare_agent_hook_governance.py tests/unit/test_dare_agent_hook_transport_boundary.py`: passed (`39 passed, 1 warning`) after the new unit tests landed, confirming no regression on the previously accepted A-101 coverage surface.
+
+### Behavior Verification
+
+- Happy path: `_internal` execute logic now has a direct test proving model responses without tool calls finalize successfully and persist the assistant message into STM without going back through the `DareAgent` façade.
+- Happy path: `_internal` tool execution now has a direct retry test proving `done_predicate` retries until the required output key is produced, while preserving the existing success result shape.
+- Error branch: `_internal` execute/model hook block, tool preflight deny, and milestone plan-policy failure now each have direct tests asserting their structured failure payloads/events rather than relying on broader integration suites to catch drift.
+
+### Risks and Rollback
+
+- Risk: these tests use lightweight fake agents rather than full `DareAgent` instances, so future internal protocol expansion may require updating the fakes alongside implementation changes.
+- Rollback: revert the new direct unit tests and tasks/docs evidence updates; production runtime behavior is unchanged by this slice.
+
+### Review and Merge Gate Links
+
+- Historical implementation PR (merged): `https://github.com/zts212653/Deterministic-Agent-Runtime-Engine/pull/117`
+- Historical owner feedback thread: `https://github.com/zts212653/Deterministic-Agent-Runtime-Engine/pull/117`

openspec/changes/refactor-dare-agent-structure-split/tasks.md

@@ -13,7 +13,10 @@
 
 ## 3. Verification and regression protection
 
-- [ ] 3.1 Add/adjust targeted unit tests for extracted execution units (success/failure/approval/policy/retry branches).
+- [x] 3.1 Add/adjust targeted unit tests for extracted execution units (success/failure/approval/policy/retry branches).  
+  Evidence: `tests/unit/test_dare_agent_orchestration_split.py`（新增 execute hook-policy block、execute no-tool success、tool preflight deny、tool done-predicate retry、milestone plan-policy failure 五条 direct unit tests，直接覆盖 `_internal` 模块而非仅 facade delegation）  
+  Commands: `../../.venv/bin/python -m pytest -q tests/unit/test_dare_agent_orchestration_split.py -k 'before_model_hook_blocks or no_tool_calls or preflight_denies or done_predicate_is_satisfied or plan_policy_failure'` => `4 passed, 5 deselected, 1 warning`；`../../.venv/bin/python -m pytest -q tests/unit/test_dare_agent_orchestration_split.py` => `9 passed, 1 warning`；`../../.venv/bin/python -m pytest -q tests/unit/test_five_layer_agent.py tests/unit/test_dare_agent_hook_governance.py tests/unit/test_dare_agent_hook_transport_boundary.py` => `39 passed, 1 warning`  
+  Last Updated: `2026-03-03`
 - [x] 3.2 Run affected unit test suites for agent execute/tool/milestone paths and fix regressions.
 - [x] 3.3 Run design-doc drift and compile checks to ensure governance and structural integrity remain green.