Fix/qa defects df002 df011 (#9)

## Summary

What changed and why?

## Change Type

- [ ] 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: thanhnv <thanhnv.ip@gmail.com>
Co-authored-by: Vu Dam Tuan <vudt15@fpt.com>
Reviewed-on: #9

presentation/shell/main_window.py

@@ -212,6 +212,11 @@ class MainWindow(NavRailMixin, RailProjectMixin, TopBarMixin,
             self._set_nav_width_range(_NAV_MIN_WIDTH, self._nav_max_width())
         # Keep the floating Help assistant pinned to the bottom-right corner.
         if getattr(self, "help_agent", None) is not None:
+            # The Cowork composer can wrap an extra control row as the window
+            # narrows/widens, which changes how much bottom guard the dock
+            # needs — recompute it on every resize, not just reposition with
+            # whatever guard height was last measured at tab-entry time.
+            self._update_dock_guard()
             self.help_agent.reposition()
 
     def showEvent(self, event):  # noqa: N802 - Qt override

presentation/shell/nav_rail.py

@@ -81,7 +81,7 @@ class NavRailMixin:
         # 16px icon up with the nav items' icons below (1px list frame + item
         # padding) — same indent level, same icon size as e.g. Dashboard.
         toggle_row = QHBoxLayout()
-        toggle_row.setContentsMargins(0, 8, 10, 8)
+        toggle_row.setContentsMargins(10, 8, 10, 8)
         toggle_row.addWidget(self._nav_toggle_btn, 0, Qt.AlignLeft)
         toggle_row.addStretch(1)
         nvl.addLayout(toggle_row)
@@ -111,7 +111,7 @@ class NavRailMixin:
         self.nav_project_btn.menu().aboutToShow.connect(self._fill_rail_project_menu)
         self.nav_project_btn.setVisible(False)
         head = QVBoxLayout()
-        head.setContentsMargins(6, 0, 6, 6)
+        head.setContentsMargins(10, 0, 10, 6)
         head.setSpacing(6)
         head.addWidget(self.nav_project)
         head.addWidget(self.nav_project_btn)
@@ -136,7 +136,7 @@ class NavRailMixin:
         self._nav_scroll.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
         scroll_body = QWidget()
         sv = QVBoxLayout(scroll_body)
-        sv.setContentsMargins(0, 0, 0, 0)
+        sv.setContentsMargins(6, 0, 6, 0)
         sv.setSpacing(0)
         sv.addWidget(self.nav, 0)
         # RECENTS — the threads of the project named in the picker above, right

presentation/shell/rail_metrics.py

@@ -13,7 +13,7 @@ from PySide6.QtWidgets import QStyledItemDelegate
 # ---- kích thước ---------------------------------------------------------
 _NAV_EXPANDED_WIDTH = 150
 _NAV_COLLAPSED_WIDTH = 54
-_NAV_ROW_INSET = 4
+_NAV_ROW_INSET = 8
 _NAV_ROW_GAP = 6
 _NAV_MIN_WIDTH = 132
 _NAV_MAX_SHARE = 0.22