Feature/delta team/epic r04 (#7)

## Summary

epic r04 - begin refactor

## Change Type

- [x] Cowork feature
- [ ] Bug fix
- [ ] Core AI contribution
- [ ] Test / hardening
- [ ] Performance
- [ ] Documentation

## Related Work

Cowork Task:

Core Repo: http://34.143.229.138/gitea-admin/fsg-ai-core-assets

Core AI Issue:

Core Task:

Related PR:

## Scope

What is intentionally included?

What is intentionally NOT included?

## Validation

- [ ] Unit tests
- [ ] Integration tests
- [ ] Manual verification
- [ ] Regression check

Commands / evidence:

## Security Impact

Permission / credential / network / customer data impact:

## Compatibility

- [ ] No breaking change
- [ ] Breaking change documented

## Reviewer Notes

Anything Cowork reviewers should pay attention to.

---------

Co-authored-by: Anh Tran Nguyen Minh <anhtnm1@fpt.com>
Co-authored-by: Huong Le Thi Thien <huongltt35@fpt.com>
Co-authored-by: Nam Pham Dinh Thanh <nampdt@fpt.com>
Co-authored-by: Vu Dam Tuan <vudt15@fpt.com>
Co-authored-by: Hiep Ha Van <hiephv3@fpt.com>
Co-authored-by: Lam Hoang Van <lamhv7@fpt.com>
Reviewed-on: #7
Co-authored-by: Duy Le Huu <duylh19@fpt.com>

tests/unit/test_ai_task_planner_service.py

@@ -0,0 +1,87 @@
+"""EPIC R07-T05: AiTaskPlannerService — AI-generate + import, no Qt, no network.
+
+``core/ai_task_planner.py::plan_tasks`` and ``core/task_import.py::
+import_tasks`` are exercised through a FakeProvider / real tmp files rather
+than reimplemented — this service is a seam, not a new planner.
+"""
+from __future__ import annotations
+
+import json
+
+import pytest
+
+from cowork_local.application.scheduling.ai_task_planner_service import (
+    AiTaskPlannerService,
+)
+from tests.fakes import FakeProvider, ScriptedTurn
+
+_PLAN_REPLY = json.dumps({
+    "tasks": [
+        {"title": "Draft report", "description": "d", "task_type": "cowork",
+         "priority": "medium", "schedule": {"enabled": False}}
+    ]
+})
+
+
+def test_plan_uses_the_constructor_injected_provider_factory():
+    provider = FakeProvider([ScriptedTurn(text=_PLAN_REPLY)])
+    service = AiTaskPlannerService(provider_factory=lambda: provider)
+
+    tasks = service.plan("Write a weekly report")
+
+    assert len(tasks) == 1
+    assert tasks[0]["title"] == "Draft report"
+    assert provider.call_count == 1
+
+
+def test_plan_prefers_an_explicit_provider_over_the_factory():
+    factory_provider = FakeProvider([ScriptedTurn(text=_PLAN_REPLY)], strict=False)
+    explicit_provider = FakeProvider([ScriptedTurn(text=_PLAN_REPLY)])
+    service = AiTaskPlannerService(provider_factory=lambda: factory_provider)
+
+    service.plan("Write a weekly report", provider=explicit_provider)
+
+    assert explicit_provider.call_count == 1
+    assert factory_provider.call_count == 0
+
+
+def test_plan_without_any_provider_raises_runtime_error():
+    service = AiTaskPlannerService(provider_factory=None)
+    with pytest.raises(RuntimeError):
+        service.plan("Write a weekly report")
+
+
+def test_plan_stamps_attachments_onto_every_generated_task():
+    two_tasks_reply = json.dumps({"tasks": [
+        {"title": "A", "task_type": "cowork"},
+        {"title": "B", "task_type": "cowork"},
+    ]})
+    provider = FakeProvider([ScriptedTurn(text=two_tasks_reply)])
+    service = AiTaskPlannerService(provider_factory=lambda: provider)
+
+    tasks = service.plan("do two things", file_paths=["a.txt"], links=["https://x"])
+
+    assert len(tasks) == 2
+    for t in tasks:
+        assert t["input"]["file_paths"] == ["a.txt"]
+        assert t["input"]["links"] == ["https://x"]
+
+
+def test_import_file_delegates_to_core_task_import(tmp_path):
+    csv_path = tmp_path / "tasks.csv"
+    csv_path.write_text("title,task_type,priority\nMy Task,cowork,medium\n", encoding="utf-8")
+    service = AiTaskPlannerService()
+
+    tasks = service.import_file(csv_path)
+
+    assert len(tasks) == 1
+    assert tasks[0]["title"] == "My Task"
+
+
+def test_import_file_raises_value_error_on_unsupported_extension(tmp_path):
+    bogus = tmp_path / "tasks.txt"
+    bogus.write_text("nope", encoding="utf-8")
+    service = AiTaskPlannerService()
+
+    with pytest.raises(ValueError):
+        service.import_file(bogus)