test: add tests for setup wizard personalization and system prompt builder

Cover _USE_CASE_PLUGINS mapping, _suggest_plugins side effects, _build_system_base
output for all name/purpose combinations, and GeneralConfig.purpose round-trip.
Also update CLAUDE.md with the testing workflow rule.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/unit/test_chat_history.py

@@ -88,3 +88,70 @@ def test_trim_to_budget_no_trim_when_under_budget():
 def test_trim_to_budget_empty_list():
     from pyra.chat.history import _trim_to_budget
     assert _trim_to_budget([], 1000) == []
+
+
+# ── _build_system_base tests ───────────────────────────────────────────────────
+
+def test_build_system_base_default_identity():
+    from pyra.chat.history import _build_system_base
+    result = _build_system_base("User", "Pyra", "")
+    assert "You are Pyra" in result
+    assert "User" in result
+
+
+def test_build_system_base_custom_name_and_assistant():
+    from pyra.chat.history import _build_system_base
+    result = _build_system_base("Alice", "Aria", "")
+    assert "You are Aria" in result
+    assert "Alice" in result
+
+
+def test_build_system_base_no_purpose_omits_focus_block():
+    from pyra.chat.history import _build_system_base
+    result = _build_system_base("User", "Pyra", "")
+    assert "primary purpose" not in result
+    assert "not a general-purpose chatbot" not in result
+
+
+def test_build_system_base_with_purpose_includes_focus_block():
+    from pyra.chat.history import _build_system_base
+    result = _build_system_base("User", "Pyra", "manage my Nextcloud server")
+    assert "primary purpose" in result
+    assert "manage my Nextcloud server" in result
+    assert "not a general-purpose chatbot" in result
+
+
+def test_build_system_base_always_includes_security_constraints():
+    from pyra.chat.history import _build_system_base
+    for purpose in ("", "manage servers"):
+        result = _build_system_base("User", "Pyra", purpose)
+        assert "vault" in result
+        assert "shell commands" in result
+
+
+def test_build_for_api_uses_config_user_name(tmp_pyra_home, monkeypatch):
+    monkeypatch.setattr("pyra.chat.history.load_context_for_session", lambda: "")
+    from pyra.config.schema import PyraConfig, ProviderConfig, GeneralConfig
+    from pyra.chat.history import ConversationHistory
+    cfg = PyraConfig(
+        ai=ProviderConfig(provider_id="lmstudio", model="gemma"),
+        general=GeneralConfig(user_name="Alice", assistant_name="Aria", purpose=""),
+    )
+    h = ConversationHistory(cfg)
+    system = h.build_for_api()[0]["content"]
+    assert "Alice" in system
+    assert "Aria" in system
+
+
+def test_build_for_api_uses_purpose(tmp_pyra_home, monkeypatch):
+    monkeypatch.setattr("pyra.chat.history.load_context_for_session", lambda: "")
+    from pyra.config.schema import PyraConfig, ProviderConfig, GeneralConfig
+    from pyra.chat.history import ConversationHistory
+    cfg = PyraConfig(
+        ai=ProviderConfig(provider_id="lmstudio", model="gemma"),
+        general=GeneralConfig(purpose="manage my home server"),
+    )
+    h = ConversationHistory(cfg)
+    system = h.build_for_api()[0]["content"]
+    assert "manage my home server" in system
+    assert "primary purpose" in system