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>

presentation/graph/graph_messages_view.py

@@ -0,0 +1,110 @@
+"""GraphMessagesView — the "Messages by day" tab of GraphRAG (R08-T14, split
+out of ``graph_renderer.py`` to keep that file under the 400-line cap;
+originally ``ui/structure_graph_view.py``, lines 427-497 of the original
+1035-line file: ``_on_view_tab``, ``_toggle_messages``, ``_reload_messages``,
+``_show_msg_json``).
+
+A plain (non-Qt-widget) helper composed BY ``GraphRenderer`` — same
+composition-to-respect-the-line-cap pattern as
+``office_document_renderer.py``. Owns the ``QTreeWidget`` itself (built
+here, added to the owner's stack at construction) since nothing else needs
+it, but reaches into ``owner._stack``/``owner.web``/``owner.view``/
+``owner.active_project_id`` to switch the shared stack and scope by project.
+"""
+from __future__ import annotations
+
+from collections import OrderedDict
+
+from PySide6.QtCore import Qt
+from PySide6.QtWidgets import QTreeWidget, QTreeWidgetItem
+
+from cowork_local.i18n import tr
+
+
+class GraphMessagesView:
+    """Tab "Tin nhắn" của GraphRAG: cây hội thoại gom theo ngày, bấm vào xem JSON.
+
+    Một helper thuần (không phải widget) do ``GraphRenderer`` sở hữu; nó tự dựng
+    cây và đưa vào stack dùng chung của chủ sở hữu.
+    """
+    def __init__(self, owner) -> None:
+        """Dựng cây tin nhắn và đưa vào stack dùng chung của chủ sở hữu — helper thuần,
+        không phải widget độc lập.
+        """
+        self._owner = owner
+        self.widget = QTreeWidget()
+        self.widget.setHeaderHidden(True)
+        self.widget.itemClicked.connect(self._show_msg_json)
+        owner._stack.addWidget(self.widget)
+
+    def on_view_tab(self, index: int) -> None:
+        """Tab 0 = graph, tab 1 = messages."""
+        o = self._owner
+        if index == 1:
+            self.reload()
+            o._stack.setCurrentWidget(self.widget)
+        else:
+            o._stack.setCurrentWidget(o.web if o.web is not None else o.view)
+
+    def toggle(self) -> None:
+        """Kept for callers that still ask for a flip (e.g. keyboard paths)."""
+        o = self._owner
+        showing = o._stack.currentWidget() is self.widget
+        o.view_tabs.setCurrentIndex(0 if showing else 1)
+
+    def reload(self) -> None:
+        """Build the tree: day -> conversation. Click a conversation to see
+        its messages as JSON. Scoped to the current project's history."""
+        from cowork_local.core.history import list_conversations
+
+        o = self._owner
+        self.widget.clear()
+        pid = o.active_project_id or ""
+        by_day: "OrderedDict[str, list]" = OrderedDict()
+        try:
+            convs = list_conversations(o.ctx.config.history_dir())
+        except Exception:  # noqa: BLE001
+            convs = []
+        for conv in convs:
+            if pid and conv.get("project_id", "default") != pid:
+                continue
+            day = (conv.get("created") or "")[:10] or "—"
+            by_day.setdefault(day, []).append(conv)
+        if not by_day:
+            self.widget.addTopLevelItem(QTreeWidgetItem([tr("structure.msgs_none")]))
+            return
+        for day in sorted(by_day, reverse=True):
+            convs_d = by_day[day]
+            day_item = QTreeWidgetItem([f"{day}   ({len(convs_d)})"])
+            for conv in convs_d:
+                it = QTreeWidgetItem([conv.get("title", "(untitled)")])
+                it.setData(0, Qt.UserRole, str(conv.get("path", "")))
+                day_item.addChild(it)
+            self.widget.addTopLevelItem(day_item)
+            day_item.setExpanded(True)
+
+    def _show_msg_json(self, item, _col: int = 0) -> None:
+        """Bấm một hội thoại trong cây: hiện toàn bộ nội dung của nó dưới dạng JSON đã
+        thoát HTML ở khung chi tiết.
+        """
+        import html
+        import json
+
+        from cowork_local.core.history import load_conversation
+        path = item.data(0, Qt.UserRole)
+        if not path:
+            return
+        try:
+            conv = load_conversation(path)
+            payload = {"title": conv.get("title", ""), "created": conv.get("created", ""),
+                       "kind": conv.get("kind", ""), "project_id": conv.get("project_id", ""),
+                       "messages": conv.get("messages", [])}
+            text = json.dumps(payload, ensure_ascii=False, indent=2)
+        except Exception as exc:  # noqa: BLE001
+            text = f"(could not read: {exc})"
+        self._owner.raw_json_ready.emit(
+            f'<pre style="white-space:pre-wrap; font-family:Consolas,monospace; '
+            f'font-size:12px;">{html.escape(text)}</pre>')
+
+
+__all__ = ["GraphMessagesView"]