Co4E step config as collapsible sections; tighter Kanban lanes; Output panel fills its column

- co4e_config_panel: StepConfigPanel reorganized into four collapsible,
  borderless sections (Co ban / Model & Quyen / Skills & Tep / Agent song
  song) instead of one long form. Agent song song is its own section,
  shown only for parallel-variant steps. Fixes a QVBoxLayout without a
  trailing stretch that was handing every section an equal share of the
  scroll area's leftover height instead of sizing to content.
- schedule_task_tab / theme: Kanban board lane gutters and per-lane
  margins trimmed so the seven lanes read their card content more
  clearly on a laptop-width window.
- chat_panel / widgets: the Output Files list in Cowork/Code no longer
  stops at a fixed height with empty panel below it - it now fills the
  column down to the composer.
- composer: Attach/Send/Stop buttons match the input box's height and
  align to its top/bottom edge instead of floating centered beside it.
- app.py: the sidebar's "All projects" link reads as a link (italic,
  accent color) instead of a plain row.
- i18n: labels for the three renamed Co4E section headers (VI/EN/JA).

ui/schedule_task_tab.py

@@ -133,14 +133,25 @@ class ScheduleTaskTab(QWidget):
         board = QWidget()
         scroll.setWidget(board)
         cols = QHBoxLayout(board)
-        cols.setSpacing(8)
+        # Gutters wide enough to read as a break between lanes without eating
+        # too much of the seven-way split — they still share the board equally
+        # (see _fit_lanes below), so a wider gutter narrows every lane by the
+        # same share automatically; nothing else to compute here.
+        cols.setSpacing(2)
         self.columns: Dict[str, _KanbanColumn] = {}
         self.column_headers: Dict[str, QLabel] = {}
         for status in STATUSES:
             box = QVBoxLayout()
+            # The per-lane holder's own margins were the style's default
+            # (~9px a side) on top of the inter-column gap — with seven lanes
+            # that outweighs the gap itself. Zero it out and let the lane's
+            # header/list fill the width _fit_lanes() hands them.
+            box.setContentsMargins(0, 0, 0, 0)
+            box.setSpacing(2)
             head = QLabel()
             head.setStyleSheet("font-weight:600;")
             col = _KanbanColumn(status)
+            col.setObjectName("kanbanLane")
             col.task_dropped.connect(self._on_task_dropped)
             col.itemDoubleClicked.connect(self._on_double_click)
             col.setContextMenuPolicy(Qt.CustomContextMenu)