core/cli: one-shot chat with -p/stdin and exit codes

Add plyngent chat -p/--prompt (and non-TTY stdin), --stream/--no-stream,
--yes, --quiet. Non-interactive mode uses NonInteractiveBackend and
disables limit prompts. Exit codes: 0 ok, 1 config, 2 cancelled, 3 failed.

tests/test_cli/test_oneshot.py

@@ -0,0 +1,159 @@
+from __future__ import annotations
+
+from pathlib import Path
+from typing import TYPE_CHECKING, Literal, overload
+
+import pytest
+from click.testing import CliRunner
+
+from plyngent.cli.app import _read_prompt_text, main
+from plyngent.cli.exit_codes import EXIT_OK
+from plyngent.lmproto.openai_compatible.model import (
+    AssistantChatMessage,
+    ChatCompletionChoice,
+    ChatCompletionChunk,
+    ChatCompletionResponse,
+    ChatCompletionsParam,
+)
+
+if TYPE_CHECKING:
+    from collections.abc import AsyncIterator
+
+
+def test_read_prompt_flag_only() -> None:
+    assert _read_prompt_text("hello", stdin_isatty=True) == "hello"
+    assert _read_prompt_text("  ", stdin_isatty=True) is None
+    assert _read_prompt_text(None, stdin_isatty=True) is None
+
+
+def test_read_prompt_stdin(monkeypatch: pytest.MonkeyPatch) -> None:
+    class FakeStdin:
+        def read(self) -> str:
+            return "from stdin\n"
+
+    monkeypatch.setattr("plyngent.cli.app.sys.stdin", FakeStdin())
+    assert _read_prompt_text(None, stdin_isatty=False) == "from stdin"
+    assert _read_prompt_text("flag", stdin_isatty=False) == "flag\nfrom stdin"
+
+
+def test_chat_oneshot_requires_provider_flags(tmp_path: Path) -> None:
+    config = tmp_path / "plyngent.toml"
+    _ = config.write_text(
+        """
+[providers.a]
+preset = "openai-compatible"
+url = "https://example.com/v1"
+access_key_or_token = "sk"
+
+[providers.a.models]
+"m1" = {}
+
+[providers.b]
+preset = "openai-compatible"
+url = "https://example.com/v1"
+access_key_or_token = "sk"
+
+[providers.b.models]
+"m2" = {}
+""",
+        encoding="utf-8",
+    )
+    runner = CliRunner()
+    result = runner.invoke(
+        main,
+        ["chat", "--config", str(config), "-p", "hi", "--workspace", str(tmp_path)],
+    )
+    assert result.exit_code != 0
+    assert "provider" in result.output.lower() or "provider" in (result.stderr or "").lower()
+
+
+def test_chat_oneshot_success(tmp_path: Path, monkeypatch: pytest.MonkeyPatch) -> None:
+    config = tmp_path / "plyngent.toml"
+    _ = config.write_text(
+        """
+[providers.local]
+preset = "openai-compatible"
+url = "https://example.com/v1"
+access_key_or_token = "sk"
+
+[providers.local.models]
+"tiny" = {}
+""",
+        encoding="utf-8",
+    )
+
+    class DummyClient:
+        @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 param
+            if stream:
+
+                async def empty() -> AsyncIterator[ChatCompletionChunk]:
+                    if False:
+                        yield  # type: ignore[misc]
+                    return
+
+                return empty()
+            return ChatCompletionResponse(
+                id="1",
+                object="chat.completion",
+                created=0,
+                model="tiny",
+                choices=[
+                    ChatCompletionChoice(
+                        index=0,
+                        message=AssistantChatMessage(content="pong"),
+                        logprobs={},
+                        finish_reason="stop",
+                    )
+                ],
+                system_fingerprint="",
+                usage={},
+            )
+
+    monkeypatch.setattr("plyngent.cli.app.create_client", lambda _p: DummyClient())
+    monkeypatch.setattr(
+        "plyngent.cli.state.create_client",
+        lambda _p: DummyClient(),
+    )
+
+    runner = CliRunner()
+    result = runner.invoke(
+        main,
+        [
+            "chat",
+            "--config",
+            str(config),
+            "--provider",
+            "local",
+            "--model",
+            "tiny",
+            "-p",
+            "ping",
+            "--no-stream",
+            "--workspace",
+            str(tmp_path),
+            "--quiet",
+        ],
+    )
+    assert result.exit_code == EXIT_OK
+    assert "pong" in result.output
+
+
+def test_chat_help_mentions_prompt() -> None:
+    runner = CliRunner()
+    result = runner.invoke(main, ["chat", "--help"])
+    assert result.exit_code == 0
+    assert "--prompt" in result.output or "-p" in result.output
+    assert "Exit codes" in result.output or "one-shot" in result.output.lower()