fix(cli): honor workspace_dir from config.yaml when --workspace not provided (#90)

[draix]

Summary

Fixes #90 — workspace_dir configured in config.yaml is ignored by the CLI mode.

When the user does not pass --workspace, the CLI currently falls back directly to Path.cwd() and never reads workspace_dir from config.yaml. This PR makes the CLI honour the same precedence the ACP adapter already uses:

--workspace (CLI) > workspace_dir (config.yaml) > Path.cwd()

Reproduction (from the issue)

config.yaml:

workspace_dir: "./workspace"

Run:

python -m mini_agent.cli

Before this PR:

Workspace: D:\2026\Mini-Agent

Expected (and after this PR):

Workspace: D:\2026\Mini-Agent\workspace

What changed

• mini_agent/cli.py

  • New resolve_workspace_dir(cli_workspace, config) helper that implements the precedence: CLI arg > config.agent.workspace_dir > Path.cwd(). It expands ~ and resolves relative paths against the current cwd, so ./workspace becomes <cwd>/workspace — matching the behaviour described in the issue.
  • main() no longer pre-resolves the workspace path before the config is loaded. Instead it passes the raw args.workspace (or None) to run_agent(), which resolves the final workspace right after loading the config.
  • This mirrors the pattern already used in mini_agent/acp/__init__.py::MiniMaxACPAgent.newSession:

    workspace = Path(params.cwd or self._config.agent.workspace_dir).expanduser()

    so CLI and ACP entrypoints now behave consistently.

• tests/test_cli_workspace.py (new)

  • --workspace wins over config.workspace_dir.
  • Without --workspace, the value from config.yaml is used.
  • Relative ./workspace in config resolves against the current cwd (regression test for the exact repro in config.yaml中的workspace_dir 配置在 CLI 模式下未生效 #90).
  • Empty workspace_dir in config falls back to Path.cwd().
  • ~/... in workspace_dir is expanded to the user home directory.

Test plan

$ uv run pytest tests/test_cli_workspace.py -v
...
5 passed in 0.29s

Full test suite was also run; the pre-existing failures on main (missing mini_agent/config/config.yaml, API keys, and an unrelated pydantic issue in test_acp_invalid_session) are not introduced by this PR.

Notes

• No behaviour change when --workspace is provided.
• No behaviour change for users who do not set workspace_dir in config.yaml — Path.cwd() is still the last-resort default.
• The Path.mkdir(parents=True, exist_ok=True) call previously made by main() is preserved inside run_agent() after the workspace is resolved.

Closes #90