feat(R08): split ScheduleTaskTab, FolderTab, DashboardTab, StructureGraphView

Team Hoa, EPIC R08 (UI/Application Separation) - Team Hoa scope only
(R08-T11 -> T14; R08-T01->T10 belong to Team Duy/Team Nam).

- R08-T11: ui/schedule_task_tab.py (795 lines) -> presentation/scheduling/
  {kanban_board_widget,calendar_view_widget,ai_task_creator_dialog,
  ai_task_import_dialog,run_history_dialog}.py + schedule_task_tab.py
  shell. Kanban CRUD/drag-drop now goes through
  application/scheduling/task_application_service.py (R07-T04) instead of
  ~30 lines of inline if/elif per drag target.
- R08-T12: ui/folder_tab.py (1587 lines, the largest of the four) ->
  presentation/folder/{workspace_file_tree,document_preview_manager,
  code_editor,office_document_renderer,ai_file_editor_dialog,
  ai_edit_model_resolver,ai_edit_pipeline}.py + folder_tab.py shell.
  Closes the R06-T05 loop: FileWorkspaceService existed since R06 with
  zero production call sites (confirmed by grep); every plain-text write
  (save/create/write_content) now goes through it, gaining path
  containment and a Python-syntax warning the original code never had.
  Pure helpers (_read_text, _is_probably_text, _pptx_available,
  _split_code_block, _parse_ai_output) moved to
  application/workspaces/{file_preview_helpers,ai_edit_output}.py.
- R08-T13: ui/dashboard_tab.py (437 lines) -> presentation/dashboard/
  {token_usage_card_widget,usage_chart_widget,habits_widget}.py +
  dashboard_tab.py shell, backed by a new
  application/monitoring/dashboard_query_service.py (pricing/period/
  summary queries the three widgets used to each recompute separately).
  Directory-ownership note left in the checklist for Team Nam.
- R08-T14: ui/structure_graph_view.py (1035 lines) ->
  presentation/graph/{graph_scene_items,graph_renderer,
  graph_messages_view,graph_qa_widget}.py + structure_graph_view.py
  shell. Extraction helpers (_pdf_to_markdown, _extract_file_contents)
  moved to application/workspaces/graph_index_service.py (pure Python).
  Renderer and Q&A panel talk only through signals
  (node_selected/graph_rendered/raw_json_ready/project_changed) - neither
  imports the other.
- presentation/shared/web_engine_support.py: HAS_WEB_ENGINE, previously
  duplicated (folder_tab imported it FROM structure_graph_view.py) - now
  one shared flag instead of one screen importing another screen's module.

All four old ui/*.py files deleted; app.py and ui/workspace_tab.py updated
to the new import paths (each god-file only had 1-2 real construction
sites, so import sites were updated directly rather than kept as a
strangler-fig shim - unlike core/tools.py at R05, which had dozens).

pytest: 377 pass (+94 vs the R07 baseline of 328; same 4 pre-existing
failures as the R05/R06 baseline, unrelated to this work).
scripts/check_imports.py: PASS. python -c "import cowork_local.app": OK.
Every new file < 400 lines (largest: graph_renderer.py, 391).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

presentation/dashboard/habits_widget.py

@@ -0,0 +1,171 @@
+"""HabitsWidget — the usage-habits summary + AI recommendations panel of the
+Dashboard (R08-T13, extracted from ``ui/dashboard_tab.py::DashboardTab``,
+lines 154-184/348-372/376-438 of the original 437-line file: the habits/AI
+layout, ``refresh()``'s habits-HTML section, ``_apply_saving_strategy``,
+``_ai_analyze``).
+"""
+from __future__ import annotations
+
+from datetime import date
+from typing import List, Optional
+
+from PySide6.QtWidgets import QHBoxLayout, QLabel, QPushButton, QTextBrowser, QVBoxLayout, QWidget
+from PySide6.QtCore import Signal
+
+from cowork_local.application.monitoring import DashboardQueryService
+from cowork_local.core.worker import AgentWorker
+from cowork_local.i18n import tr
+from cowork_local.ui.icons import icon
+from cowork_local.ui.widgets import fmt_tokens
+
+
+class HabitsWidget(QWidget):
+    status_message = Signal(str)
+
+    def __init__(self, ctx, query: DashboardQueryService, parent=None):
+        super().__init__(parent)
+        self.ctx = ctx
+        self._query = query
+        self._ai_worker: Optional[AgentWorker] = None
+        self._period_range = (None, None)   # set on each refresh(); _ai_analyze reuses it
+
+        root = QVBoxLayout(self)
+        root.setContentsMargins(0, 0, 0, 0)
+        self._habits_title = QLabel()
+        self._habits_title.setStyleSheet("font-weight:600;")
+        habits_head = QHBoxLayout()
+        self.ai_analyze_btn = QPushButton()
+        self.ai_analyze_btn.setIcon(icon("sparkle"))
+        self.ai_analyze_btn.clicked.connect(self._ai_analyze)
+        # Apply an AI-suggested cost-saving strategy — only after the user
+        # clicks to approve it.
+        self.apply_strategy_btn = QPushButton()
+        self.apply_strategy_btn.setIcon(icon("bolt"))
+        self.apply_strategy_btn.setVisible(False)
+        self.apply_strategy_btn.clicked.connect(self._apply_saving_strategy)
+        habits_head.addWidget(self._habits_title, 1)
+        habits_head.addWidget(self.apply_strategy_btn)
+        habits_head.addWidget(self.ai_analyze_btn)
+        root.addLayout(habits_head)
+        self.habits = QTextBrowser()
+        self.habits.setOpenExternalLinks(False)
+        self.habits.setMinimumHeight(160)
+        root.addWidget(self.habits, 1)
+        self._ai_title = QLabel()
+        self._ai_title.setStyleSheet("font-weight:600;")
+        self._ai_title.setVisible(False)
+        root.addWidget(self._ai_title)
+        self.ai_advice = QTextBrowser()
+        self.ai_advice.setOpenExternalLinks(False)
+        self.ai_advice.setMinimumHeight(140)
+        self.ai_advice.setVisible(False)
+        root.addWidget(self.ai_advice, 1)
+
+        self.retranslate()
+
+    def retranslate(self) -> None:
+        self.ai_analyze_btn.setText(tr("dashboard.ai_analyze_btn"))
+        self.ai_analyze_btn.setToolTip(tr("dashboard.ai_analyze_tooltip"))
+        self.apply_strategy_btn.setText(tr("dashboard.strategy_btn"))
+        self.apply_strategy_btn.setToolTip(tr("dashboard.strategy_tooltip"))
+        self._habits_title.setText(tr("dashboard.habits_title"))
+
+    def refresh(self, start: date, end: date) -> None:
+        self._period_range = (start, end)
+        summary = self._query.summary(start, end)
+        s, events = summary["stats"], summary["events"]
+
+        lines: List[str] = []
+        if not events:
+            lines.append(f"<i>{tr('dashboard.no_data')}</i>")
+        else:
+            lines.append(f"<b>{tr('dashboard.h_top')}</b>")
+            lines.append("<ol>")
+            for label, tok in s["top_labels"]:
+                pct = int(tok * 100 / s["total"]) if s["total"] else 0
+                lines.append(f"<li>{label[:60]} — {fmt_tokens(tok)} tokens ({pct}%)</li>")
+            lines.append("</ol>")
+            src_parts = ", ".join(
+                f"{tr(f'app.tab.{k}') if k in ('cowork', 'code') else k}: {fmt_tokens(v)}"
+                for k, v in s["by_source"])
+            lines.append(f"<b>{tr('dashboard.h_by_source')}</b>: {src_parts}<br>")
+            lines.append(f"<b>{tr('dashboard.h_avg')}</b>: "
+                         f"{fmt_tokens(s['avg_per_turn'])} tokens<br>")
+            if s["busiest_day"]:
+                lines.append(f"<b>{tr('dashboard.h_busiest_day')}</b>: {s['busiest_day']}<br>")
+            if s["busiest_hour"] is not None:
+                lines.append(f"<b>{tr('dashboard.h_busiest_hour')}</b>: "
+                             f"{s['busiest_hour']:02d}:00–{s['busiest_hour']:02d}:59<br>")
+            if s["estimated_share"] > 0:
+                lines.append(f"<i>{tr('dashboard.estimated_note', pct=int(s['estimated_share'] * 100))}</i>")
+        self.habits.setHtml("".join(lines))
+
+    def _apply_saving_strategy(self) -> None:
+        """Apply an AI-suggested cost-saving strategy AFTER the user
+        approves: turn on auto-compress and compress earlier (lower
+        threshold) + compress content before sending it to the agent."""
+        from PySide6.QtWidgets import QMessageBox
+        if QMessageBox.question(self, tr("dashboard.strategy_title"),
+                                tr("dashboard.strategy_confirm")) != QMessageBox.Yes:
+            return
+        cx = self.ctx.config.data.setdefault("context", {})
+        cx["auto_compact"] = True
+        cx["compact_threshold"] = 0.6          # compress at 60% of the window (was ~80%)
+        cx["compress_before_send"] = True      # digest context before each turn
+        self.ctx.save()
+        self.status_message.emit(tr("dashboard.strategy_applied"))
+
+    def _ai_analyze(self) -> None:
+        """✨ Send the aggregated numbers (never raw prompt text) to the
+        active provider and show habit feedback + token-saving
+        recommendations."""
+        if self._ai_worker is not None:
+            return
+        start, end = self._period_range
+        if start is None:
+            return
+        summary = self._query.summary(start, end)
+        if not summary["events"]:
+            self.status_message.emit(tr("dashboard.no_data"))
+            return
+        stats = summary["stats"]
+        self.ai_analyze_btn.setEnabled(False)
+        self.ai_analyze_btn.setText(tr("dashboard.ai_analyzing"))
+        ctx = self.ctx
+
+        def job(worker: AgentWorker):
+            from cowork_local.core import usage_tracker as ut
+            from cowork_local.i18n import get_language
+
+            prompt = ut.build_ai_analysis_prompt(stats, get_language())
+            provider = ctx.build_active_provider()
+            reply = provider.chat([{"role": "user", "content": prompt}],
+                                  cancel=worker.stop_event)
+            return {"text": (reply.get("content") or "").strip()}
+
+        def done(result: dict) -> None:
+            self._ai_worker = None
+            self.ai_analyze_btn.setEnabled(True)
+            self.ai_analyze_btn.setText(tr("dashboard.ai_analyze_btn"))
+            text = result.get("text") or ""
+            if text:
+                self._ai_title.setText(tr("dashboard.ai_advice_title"))
+                self._ai_title.setVisible(True)
+                self.ai_advice.setMarkdown(text)
+                self.ai_advice.setVisible(True)
+                self.apply_strategy_btn.setVisible(True)
+
+        def failed(err: str) -> None:
+            self._ai_worker = None
+            self.ai_analyze_btn.setEnabled(True)
+            self.ai_analyze_btn.setText(tr("dashboard.ai_analyze_btn"))
+            self.status_message.emit(str(err))
+
+        w = AgentWorker(job)
+        w.finished_ok.connect(done)
+        w.failed.connect(failed)
+        self._ai_worker = w
+        w.start()
+
+
+__all__ = ["HabitsWidget"]