feat(task-018): add role-based context selection

tests/test_prompt.py

@@ -322,3 +322,94 @@ def test_generate_agent_prompt_with_custom_role(tmp_path: Path) -> None:
     prompt = generate_agent_prompt(tmp_path)
 
     assert "You are a devops engineer." in prompt
+
+
+def test_architecture_agent_receives_architecture_context(tmp_path: Path) -> None:
+    (tmp_path / "TASKS.md").write_text(
+        "# TASKS\n\n"
+        "## TASK-001 — First\nStatus: Done\n\n"
+        "Goal: x.\n\n"
+        "## TASK-002 — Second\nStatus: Todo\n\n"
+        "Role: Architecture Agent\n"
+        "Goal: y.\n",
+        encoding="utf-8",
+    )
+
+    prompt = generate_agent_prompt(tmp_path)
+
+    assert "context/architecture.md" in prompt
+    assert "context/product-brief.md" in prompt
+    assert "context/decisions.md" in prompt
+
+
+def test_implementation_agent_receives_implementation_context(tmp_path: Path) -> None:
+    (tmp_path / "TASKS.md").write_text(
+        "# TASKS\n\n"
+        "## TASK-001 — First\nStatus: Done\n\n"
+        "Goal: x.\n\n"
+        "## TASK-002 — Second\nStatus: Todo\n\n"
+        "Role: Implementation Agent\n"
+        "Goal: y.\n",
+        encoding="utf-8",
+    )
+
+    prompt = generate_agent_prompt(tmp_path)
+
+    assert "AGENT_HANDOFF.md" in prompt
+    assert "context/agent-guidelines.md" in prompt
+    assert "CLAUDE.md" in prompt
+
+
+def test_documentation_agent_receives_documentation_context(tmp_path: Path) -> None:
+    (tmp_path / "TASKS.md").write_text(
+        "# TASKS\n\n"
+        "## TASK-001 — First\nStatus: Done\n\n"
+        "Goal: x.\n\n"
+        "## TASK-002 — Second\nStatus: Todo\n\n"
+        "Role: Documentation Agent\n"
+        "Goal: y.\n",
+        encoding="utf-8",
+    )
+
+    prompt = generate_agent_prompt(tmp_path)
+
+    assert "TEST_PLAN.md" in prompt
+    assert "AGENT_HANDOFF.md" in prompt
+
+
+def test_context_files_differ_by_role(tmp_path: Path) -> None:
+    (tmp_path / "TASKS.md").write_text(
+        "# TASKS\n\n"
+        "## TASK-001 — First\nStatus: Done\n\n"
+        "Goal: x.\n\n"
+        "## TASK-002 — Architect\nStatus: Todo\n\n"
+        "Role: Architecture Agent\n"
+        "Goal: y.\n",
+        encoding="utf-8",
+    )
+
+    prompt = generate_agent_prompt(tmp_path)
+
+    # Architecture role should have architecture-specific files
+    assert "context/architecture.md" in prompt
+
+
+def test_no_role_uses_default_context(tmp_path: Path) -> None:
+    """When no Role is set, the default file list is used (backward compatible)."""
+    (tmp_path / "TASKS.md").write_text(
+        "# TASKS\n\n"
+        "## TASK-001 — First\nStatus: Done\n\n"
+        "Goal: x.\n\n"
+        "## TASK-002 — Second\nStatus: Todo\n\n"
+        "Goal: y.\n",
+        encoding="utf-8",
+    )
+
+    prompt = generate_agent_prompt(tmp_path)
+
+    # Default files must still be present
+    assert "README.md" in prompt
+    assert "TASKS.md" in prompt
+    assert "PROJECT_STATE.md" in prompt
+    assert "AGENT_HANDOFF.md" in prompt
+    assert "context/agent-guidelines.md" in prompt