core/cli+agent: /compact and resume latest by workspace recency

Soft-compact history, model-summarize without tools, seed a new session;
/resume with no id loads the lately-used session for this workspace.

tests/test_agent/test_compact_summarize.py

@@ -0,0 +1,111 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Literal, overload
+
+from plyngent.agent.compact import (
+    build_compacted_seed_messages,
+    format_transcript,
+    soft_compact_transcript,
+    summarize_messages,
+)
+from plyngent.lmproto.openai_compatible.model import (
+    AssistantChatMessage,
+    ChatCompletionChoice,
+    ChatCompletionChunk,
+    ChatCompletionResponse,
+    ChatCompletionsParam,
+    SystemChatMessage,
+    ToolChatMessage,
+    UserChatMessage,
+)
+
+if TYPE_CHECKING:
+    from collections.abc import AsyncIterator
+
+
+def test_format_transcript() -> None:
+    text = format_transcript(
+        [
+            UserChatMessage(content="hi"),
+            AssistantChatMessage(content="yo"),
+            ToolChatMessage(content="out", tool_call_id="1"),
+        ]
+    )
+    assert "[user] hi" in text
+    assert "[assistant] yo" in text
+    assert "[tool 1] out" in text
+
+
+def test_soft_compact_transcript_shrinks_tools() -> None:
+    big = "Z" * 2000
+    messages = [
+        UserChatMessage(content="u"),
+        ToolChatMessage(content=big, tool_call_id="1"),
+        ToolChatMessage(content="recent", tool_call_id="2"),
+    ]
+    out = soft_compact_transcript(messages, max_chars=500)
+    assert "truncated" in out or len(out) < len(big) + 50
+    assert "recent" in out
+
+
+def test_build_compacted_seed_messages() -> None:
+    seed = build_compacted_seed_messages("summary text", system_prompt="sys", source_session_id=3)
+    assert isinstance(seed[0], SystemChatMessage)
+    assert seed[0].content == "sys"
+    assert isinstance(seed[1], UserChatMessage)
+    assert "summary text" in seed[1].content
+    assert "session 3" in seed[1].content
+
+
+class SummaryClient:
+    last: ChatCompletionsParam | None
+
+    def __init__(self) -> None:
+        self.last = None
+
+    @overload
+    async def chat_completions(
+        self, param: ChatCompletionsParam, *, stream: Literal[False] = False
+    ) -> ChatCompletionResponse: ...
+
+    @overload
+    async def chat_completions(
+        self, param: ChatCompletionsParam, *, stream: Literal[True]
+    ) -> AsyncIterator[ChatCompletionChunk]: ...
+
+    async def chat_completions(
+        self, param: ChatCompletionsParam, *, stream: bool = False
+    ) -> ChatCompletionResponse | AsyncIterator[ChatCompletionChunk]:
+        del stream
+        self.last = param
+        return ChatCompletionResponse(
+            id="1",
+            object="chat.completion",
+            created=0,
+            model="t",
+            choices=[
+                ChatCompletionChoice(
+                    index=0,
+                    message=AssistantChatMessage(content="  done summary  "),
+                    logprobs={},
+                    finish_reason="stop",
+                )
+            ],
+            system_fingerprint="",
+            usage={},
+        )
+
+
+async def test_summarize_messages() -> None:
+    client = SummaryClient()
+    summary = await summarize_messages(
+        client,
+        [UserChatMessage(content="hello"), AssistantChatMessage(content="world")],
+        model="m",
+    )
+    assert summary == "done summary"
+    assert client.last is not None
+    assert client.last.model == "m"
+    from msgspec import UNSET
+
+    assert client.last.tools is UNSET