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).

i18n.py

@@ -2765,6 +2765,9 @@ STRINGS: Dict[str, Dict[str, str]] = {
         "ja": "フローとチャット — /agent:<name> または /skill:<name>",
         "vi": "Chat với flow — dùng /agent:<name> hoặc /skill:<name>"},
     "co4e.send": {"en": "Send", "ja": "送信", "vi": "Gửi"},
+    "co4e.tab_basic": {"en": "Basic", "ja": "基本", "vi": "Cơ bản"},
+    "co4e.tab_model_perm": {"en": "Model & Permission", "ja": "モデルと権限", "vi": "Model & Quyền"},
+    "co4e.tab_skills_files": {"en": "Skills & Files", "ja": "スキルとファイル", "vi": "Skills & Tệp"},
     "co4e.f_label": {"en": "Label", "ja": "ラベル", "vi": "Nhãn"},
     "co4e.f_role": {"en": "Role", "ja": "ロール", "vi": "Vai trò"},
     "co4e.f_name": {"en": "Name", "ja": "名前", "vi": "Tên"},