core/memory+cli: session rename, delete, and export

Add MemoryStore rename/delete with explicit message cleanup. Slash
commands /rename, /delete (confirm), /export md|json write transcripts
from DB; deleting the current session starts a fresh empty one.

tests/test_cli/test_export.py

@@ -0,0 +1,45 @@
+from __future__ import annotations
+
+from datetime import UTC, datetime
+
+from plyngent.cli.export import (
+    encode_session_export_json,
+    format_session_export_md,
+    session_export_payload,
+)
+from plyngent.lmproto.openai_compatible.model import AssistantChatMessage, UserChatMessage
+
+
+def test_format_session_export_md() -> None:
+    text = format_session_export_md(
+        [
+            UserChatMessage(content="hi"),
+            AssistantChatMessage(content="yo", reasoning_content="plan"),
+        ],
+        sid=7,
+        name="demo",
+        workspace="/tmp/ws",
+    )
+    assert "# Session 7: demo" in text
+    assert "## user" in text
+    assert "hi" in text
+    assert "### reasoning" in text
+    assert "plan" in text
+    assert "yo" in text
+
+
+def test_session_export_json_roundtrip() -> None:
+    messages = [UserChatMessage(content="a")]
+    now = datetime.now(UTC)
+    payload = session_export_payload(
+        sid=7,
+        name="demo",
+        workspace="/tmp/ws",
+        created_at=now,
+        updated_at=now,
+        messages=messages,
+    )
+    assert isinstance(payload, dict)
+    raw = encode_session_export_json(payload)
+    assert "7" in raw
+    assert "demo" in raw

tests/test_cli/test_repl_commands.py

@@ -116,6 +116,64 @@ async def test_tools_toggle(state: ReplState) -> None:
     assert state.tools_enabled is False
 
 
+async def test_rename_slash(state: ReplState) -> None:
+    sid = state.session_id
+    assert sid is not None
+    assert await handle_slash(state, "/rename my-chat") is True
+    row = await state.memory.get_session(sid)
+    assert row is not None
+    assert row.name == "my-chat"
+
+
+async def test_delete_slash_confirm(
+    state: ReplState,
+    capsys: pytest.CaptureFixture[str],
+) -> None:
+    from plyngent.prompting import temporary_backend
+    from tests.test_prompting import ScriptedBackend
+
+    # Delete a non-current session so SQLite cannot reuse the same sid as "current".
+    victim = state.session_id
+    assert victim is not None
+    assert await handle_slash(state, "/new keep") is True
+    current = state.session_id
+    assert current != victim
+
+    with temporary_backend(ScriptedBackend([], confirms=[False])):
+        assert await handle_slash(state, f"/delete {victim}") is True
+    assert await state.memory.get_session(victim) is not None
+    assert "cancelled" in capsys.readouterr().out
+
+    with temporary_backend(ScriptedBackend([], confirms=[True])):
+        assert await handle_slash(state, f"/delete {victim}") is True
+    assert await state.memory.get_session(victim) is None
+    assert state.session_id == current
+    out = capsys.readouterr().out
+    assert "deleted" in out
+    assert "new session" not in out
+
+
+async def test_export_slash(state: ReplState, tmp_path: Path, capsys: pytest.CaptureFixture[str]) -> None:
+    from plyngent.lmproto.openai_compatible.model import AssistantChatMessage, UserChatMessage
+
+    assert state.session_id is not None
+    _ = await state.memory.append_message(state.session_id, UserChatMessage(content="hi"))
+    _ = await state.memory.append_message(state.session_id, AssistantChatMessage(content="yo"))
+    path = tmp_path / "out.md"
+    assert await handle_slash(state, f"/export md {path}") is True
+    text = path.read_text(encoding="utf-8")
+    assert "Session" in text
+    assert "hi" in text
+    assert "yo" in text
+    assert str(path.resolve()) in capsys.readouterr().out
+
+    jpath = tmp_path / "out.json"
+    assert await handle_slash(state, f"/export json {jpath}") is True
+    raw = jpath.read_text(encoding="utf-8")
+    assert '"session_id"' in raw
+    assert "hi" in raw
+
+
 async def test_stream_toggle(state: ReplState) -> None:
     assert state.agent.stream is True
     assert await handle_slash(state, "/stream off") is True

tests/test_memory/test_store.py

@@ -98,6 +98,37 @@ async def test_session_workspace_binding(store: MemoryStore, tmp_path: object) -
     assert {s.sid for s in listed_b} == {sb.sid}
 
 
+async def test_rename_session(store: MemoryStore) -> None:
+    session = await store.create_session(name="old")
+    updated = await store.rename_session(session.sid, "  new name  ")
+    assert updated.name == "new name"
+    again = await store.get_session(session.sid)
+    assert again is not None
+    assert again.name == "new name"
+    try:
+        await store.rename_session(session.sid, "   ")
+        raise AssertionError("expected ValueError")
+    except ValueError as exc:
+        assert "non-empty" in str(exc)
+    try:
+        await store.rename_session(999_999, "x")
+        raise AssertionError("expected ValueError")
+    except ValueError as exc:
+        assert "not found" in str(exc)
+
+
+async def test_delete_session_cascades_messages(store: MemoryStore) -> None:
+    from plyngent.lmproto.openai_compatible.model import UserChatMessage
+
+    session = await store.create_session(name="gone")
+    _ = await store.append_message(session.sid, UserChatMessage(content="a"))
+    _ = await store.append_message(session.sid, UserChatMessage(content="b"))
+    assert await store.delete_session(session.sid) is True
+    assert await store.get_session(session.sid) is None
+    assert await store.list_messages(session.sid) == []
+    assert await store.delete_session(session.sid) is False
+
+
 async def test_update_session_workspace(store: MemoryStore, tmp_path: object) -> None:
     from pathlib import Path