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).

theme.py

@@ -641,6 +641,10 @@ QTreeView::item:selected, QListView::item:selected, QTableView::item:selected {
    cell on top of the selection tint above — visible as a stray light border
    on a click. The selection tint already marks "current row"; drop the rect. */
 QTreeView::item:focus, QListView::item:focus, QTableView::item:focus { outline: none; border: none; }
+/* Kanban lanes (Schedule Task): seven lanes share the board width, so a card's
+   own inset competes with the other six for space the same way the inter-lane
+   gap did — trimmed to match. */
+QListWidget#kanbanLane::item { padding: 3px 2px; }
 QHeaderView::section {
     background: $bg; color: $text_muted; border: none;
     border-bottom: 1px solid $border; padding: 7px 6px; font-weight: 600;