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/shell/rail_project.py

@@ -0,0 +1,139 @@
+"""Bộ chọn project và danh sách RECENTS trên thanh rail — R08-T10.
+
+Tách khỏi ``nav_rail.py``: thanh rail có hai phần đời sống khác hẳn nhau.
+
+Phần điểm đến (Dashboard, Workspace, Giám sát…) là **tĩnh** — dựng một lần,
+đổi khi đổi ngôn ngữ. Phần này thì **động**: đổi mỗi lần người dùng chọn
+project khác, mỗi lần một cuộc trò chuyện được tạo hay kết thúc.
+
+Trộn chung một file thì mỗi lần sửa danh sách gần đây lại phải cuộn qua toàn
+bộ phần dựng rail. Cùng kiểu mixin, xem ghi chú ở đầu ``nav_rail.py``.
+"""
+from __future__ import annotations
+
+from PySide6.QtCore import Qt
+from PySide6.QtGui import QColor
+from PySide6.QtWidgets import QTreeWidget, QTreeWidgetItem
+from ...i18n import tr
+from ...ui.widgets import tidy_popup
+from ...theme import current_palette
+
+
+
+class RailProjectMixin:
+    """Bộ chọn project + RECENTS. Trộn vào MainWindow."""
+
+    def _sync_rail_project(self, *_a) -> None:
+        """Mirror the workspace's project list/selection into the rail picker.
+
+        One-way on purpose: the project list stays the source of truth, this is
+        only a second place to see and change it.
+        """
+        if self._syncing_rail_project:
+            return
+        self._syncing_rail_project = True
+        try:
+            choices = self.workspace.project_choices()
+            current = self.workspace.selected_project_id()
+            self.nav_project.clear()
+            for name, pid in choices:
+                self.nav_project.addItem(f"📁 {name}", pid)
+            if not choices:
+                # No project yet: say so, and say what to do about it, instead of
+                # leaving an empty box and a button that silently does nothing.
+                self.nav_project.addItem(tr("app.nav.no_project"), "")
+            idx = self.nav_project.findData(current)
+            if idx >= 0:
+                self.nav_project.setCurrentIndex(idx)
+            has = bool(choices)
+            tidy_popup(self.nav_project)
+            self.nav_project.setEnabled(has)
+            self.nav_project_btn.setEnabled(has)
+            self.nav_project_btn.setToolTip(
+                self.nav_project.currentText().replace("📁 ", "")
+                if has else tr("app.nav.create_project_first"))
+            self.nav_new_chat.setEnabled(has)
+            self.nav_new_chat.setToolTip(
+                "" if has else tr("app.nav.create_project_first"))
+        finally:
+            self._syncing_rail_project = False
+    def _fill_rail_project_menu(self) -> None:
+        """Mirror the picker's items. Choosing one moves the picker, which runs
+        _on_rail_project_pick — the collapsed rail adds no second code path."""
+        menu = self.nav_project_btn.menu()
+        menu.clear()
+        for i in range(self.nav_project.count()):
+            act = menu.addAction(self.nav_project.itemText(i))
+            act.setCheckable(True)
+            act.setChecked(i == self.nav_project.currentIndex())
+            act.triggered.connect(
+                lambda _checked=False, row=i: self.nav_project.setCurrentIndex(row))
+    def _on_rail_project_pick(self, _idx: int) -> None:
+        """Chọn project ở thanh menu: chuyển workspace sang project đó.
+
+        Cờ ``_syncing_rail_project`` chặn vòng lặp khi chính workspace vừa đặt lại
+        bộ chọn này.
+        """
+        if self._syncing_rail_project:
+            return
+        pid = self.nav_project.currentData()
+        if pid:
+            self.workspace.choose_project(pid)
+    def _refresh_rail_recents(self) -> None:
+        """Re-fill the rail's recents from the active project's history."""
+        from ...ui.icons import DOT_BLUE, dot_icon
+        from ...ui.icons import icon as _icon
+
+        tree = self.nav_recents
+        blocked = tree.blockSignals(True)
+        tree.clear()
+        running = self._running_session_ids()
+        threads = self.workspace.recent_threads(self._RAIL_RECENTS)
+        for t in threads:
+            it = QTreeWidgetItem([t["title"]])
+            it.setToolTip(0, t["title"])
+            if t["session_id"] in running:
+                it.setIcon(0, dot_icon(DOT_BLUE))       # same marker as History
+            elif t["pinned"]:
+                it.setIcon(0, _icon("pin"))
+            it.setData(0, Qt.UserRole, {"path": t["path"], "kind": t["kind"]})
+            tree.addTopLevelItem(it)
+        if not threads:
+            it = QTreeWidgetItem([tr("sidebar.empty")])
+            it.setDisabled(True)
+            tree.addTopLevelItem(it)
+        # The way back to everything the rail cannot show — styled as a link
+        # (italic, accent-colored) so it reads as "go elsewhere", not another row.
+        more = QTreeWidgetItem([tr("app.nav.all_projects")])
+        more.setData(0, Qt.UserRole, {"all": True})
+        more_font = more.font(0)
+        more_font.setItalic(True)
+        more.setFont(0, more_font)
+        more.setForeground(0, QColor(current_palette().accent))
+        tree.addTopLevelItem(more)
+        tree.blockSignals(blocked)
+        self.nav_recents_hdr.setVisible(not self._nav_collapsed)
+        self.nav_recents.setVisible(not self._nav_collapsed)
+    def _on_rail_recent(self, item, _col: int = 0) -> None:
+        """Bấm một dòng trong mục GẦN ĐÂY: mở hội thoại đó, hoặc mở khung "Tất cả project…"."""
+        data = item.data(0, Qt.UserRole) or {}
+        if data.get("all"):
+            self._goto(self._ROW_WORKSPACE, self.workspace._cowork_tab_idx)
+            self.workspace.show_history_pane()
+            return
+        path = data.get("path")
+        if path:
+            self._goto(self._ROW_WORKSPACE, self.workspace._cowork_tab_idx)
+            self.workspace.open_thread(path, data.get("kind", "cowork"))
+    def _on_rail_new_chat(self) -> None:
+        """Start a new chat, from any screen.
+
+        Same call the Cowork toolbar button makes — that button stays exactly
+        where it was; this is a second entry point, not a replacement.
+        """
+        self._goto(self._ROW_WORKSPACE, None)
+        self.workspace.start_new_chat()
+        self._select_nav_row(self._ROW_WORKSPACE, self.workspace.current_subtab())
+    def _nav_new_chat_enabled(self) -> bool:
+        """Nút "chat mới" chỉ bật khi đã có ít nhất một project."""
+        return bool(self.workspace.project_choices())