Fix sidebar state persistence

[Creylay]

Summary

Fixes two related bugs in the left sidebar across the Datasets, Models, and Generative modules: (1) datasets/folders were fetched and held independently by the Datasets and Models modules, so changes made in one wouldn't show up in the other without a full remount; (2) sidebar UI state (which session/task groups and which dataset folders were expanded) lived in leaf components that unmount on every route change, so it silently reset to closed/default every time the user navigated away and back. Both are fixed by lifting the shared data into one DatasetsProvider mounted at the app root, mounting ModelsProvider/GenerativeProvider at the root too, and making the group/folder list components controlled so their open/closed state lives in these persisted contexts instead of local component state.

---

Type of Change

Check all that apply like this [x]:

• Backend change
• Frontend change
• CI / Workflow change
• Build / Packaging change
• Bug fix
• Documentation

---

Changes (by file)

• src/contexts/DatasetsContext.jsx (new): shared DatasetsProvider. The single source of truth for datasets/folders (previously duplicated in ModelsContext and DatasetsAndNotebooksContext), plus the new shared openFolderIds map that tracks which named folders are expanded.
• src/components/models/ModelsContext.jsx: consumes the shared DatasetsProvider instead of calling useDatasets/useFolders directly; re-exposes openFolderIds/setOpenFolderIds; adds persisted openSections state for the sidebar's task-group open/closed map (previously local state in ModelsLeftBar).
• src/components/custom/contexts/DatasetsAndNotebooksContext.jsx: same migration to the shared DatasetsProvider; re-exposes openFolderIds/setOpenFolderIds.
• src/components/generative/GenerativeContext.jsx: adds persisted openSections state for the sidebar's session-group open/closed map (previously local state in SessionBar).
• src/App.jsx: mounts DatasetsProvider > ModelsProvider > GenerativeProvider at the app root, above the router, so their state survives navigation instead of resetting every time /app/models or /app/generative is left and re-entered.
• src/pages/models/Models.jsx, src/pages/generative/Generative.jsx: no longer wrap their own page-scoped Provider (moved to App.jsx).
• src/components/threeSectionLayout/GroupedCollapsibleList.jsx: adds an optional controlled mode (openGroups/onOpenGroupsChange), backward-compatible with its existing uncontrolled initialOpenGroups usage.
• src/components/models/ModelsLeftBar.jsx, src/components/generative/SessionBar.jsx: read/write group open-state through their context instead of local useState, and pass it into GroupedCollapsibleList as a controlled prop; ModelsLeftBar's group-reset effect now merges (preserves already-open groups) instead of wiping all groups closed when a new task category appears, matching SessionBar's existing behavior.
• src/components/threeSectionLayout/DatasetFolderList.jsx: FolderSection gains an optional controlled open/onToggleOpen mode; the bulk-select "open everything" behavior is now a derived render-time value instead of a write into the persisted folder-open map, so entering bulk-select mode no longer permanently overwrites the user's closed folders.
• src/components/notebooks/DatasetNotebookLeftBar.jsx: passes the shared openFolderIds/setOpenFolderIds into DatasetFolderList.

---

Testing (optional)

• Rename/delete/move a dataset in one module and confirm it's reflected in the other without reloading.
• Expand a session/task group or a dataset folder, navigate away to another module and back, iit should stay expanded (previously always reset).
• Enter bulk-select mode ("select items to delete") after closing a folder/group, then exit. The folder/group should go back to closed instead of staying force-opened.