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/chat_panel.py

@@ -214,7 +214,11 @@ class ChatPanel(QWidget):
         # Right sidebar: Output files only (see below — Input is tracked but
         # not shown).
         self.input_section = CollapsibleSection(tr("widgets.input_files"))
-        self.output_section = CollapsibleSection(tr("widgets.output_files").upper())
+        # No cap: this section owns the whole right panel (its header is
+        # hoisted into io_hdr below), so the list should fill the space down
+        # to the composer instead of stopping at a fixed height with empty
+        # panel below it.
+        self.output_section = CollapsibleSection(tr("widgets.output_files").upper(), max_height=None)
         # Input files are NOT shown in Cowork's UI anymore — but they're still
         # fully tracked (add/remove/paths()) exactly as before, since that list
         # is what gets written into the conversation's own "inputs" field on
@@ -273,8 +277,7 @@ class ChatPanel(QWidget):
         bl = QVBoxLayout(bl_host)
         bl.setContentsMargins(0, 0, 0, 0)
         bl.setSpacing(4)
-        bl.addWidget(self.output_section)   # Output only — Input is tracked but hidden
-        bl.addStretch(1)
+        bl.addWidget(self.output_section, 1)   # Output only — Input is tracked but hidden; fills down to the composer
         iol.addWidget(bl_host, 1)
 
         # Collapsing shrinks the panel to a thin clickable line (not hidden).