Studio: manage chat history with projects (#5725)

* feat: align project sidebar UX with ChatGPT

* feat: align project sidebar UX with ChatGPT

* feat(chat): load stored project list

* feat(chat): add project sidebar workflows

* fix: stabilize project page navigation

* fix: projects chat loading

* fix: show project chat thread

* style: sidebar project spacing and hover clipping

* style: add expandable project chat history and move-to-project submenu

* feat: polish project sidebar

* feat: persist project sandbox paths

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* fix: only create sandbox project workspace dir

* feat: add optional project workspace deletion from delete dialog

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* fix: stabilize chat projects CI failures

* fix: polish project chat navigation

* Studio: manage chat history with projects

Group chats into projects with a dedicated projects page and route.
Sidebar shows recents with per-row actions and a vertical more-vertical
menu, and the sidebar scrollbar stays hidden so rows never shift on
hover. Includes chat settings and composer refinements.

* Studio: projects sidebar and breadcrumb polish

Sidebar:
- Remove the Compare nav item.
- Widen the sidebar to match the projects layout.
- Replace the scroll-gated bottom fade with a static fade pinned above
  the profile box, so it no longer attaches to Recents or lags the
  collapse and expand animation.

Topbar breadcrumb (chat-page):
- On a project landing show "Projects" linking to the projects list.
- Inside a project chat show the project name and chat title, with the
  project name linking back to that specific project page.
- Drop the divider between the model selector and the breadcrumb.

* Studio: make project workspace delete test cross-platform

test_chat_project_delete_files_removes_workspace rooted the project under
pytest tmp_path, which resolves to /private/tmp on macOS. The workspace
delete guard refuses paths under the system denylist by design, so the
test passed on Linux CI but failed on macOS.

Add a workspace_projects_home fixture that keeps tmp_path on Linux and
Windows (CI unchanged) and falls back to a home subdir only when the temp
root is on the platform denylist. Derive the workspace path from the
created project so it tracks the projects home.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Studio: satisfy import-hoist check for new path re-exports

documents_root and project_workspaces_root are re-exported from
utils.paths but only referenced as __all__ string literals, which the
import-hoist safety net does not count as a use. It flagged the two newly
added re-exports as unused imports and failed Source lint.

Name-load both via a module-level _REEXPORTED tuple so the check sees
them used. No behaviour change; consumers still import them from
utils.paths.

* fix: avoid projects empty-state flash

* fix: batch chat search indexing

* Studio: polish chat sidebar, run settings, and search

- Use the native OS scrollbar for the chat sidebar, Run settings panel, and chat search list instead of a custom scrollbar
- Highlight the active run in the sidebar and keep chat search available during training
- Stop the training log view from replaying when navigating back to a run
- Rename the chat settings panel to Run settings and align its toggle icon and position
- Tighten heading and sidebar letter spacing and lighten the Train and Recents labels
- Match the search dialog corner style across light and dark and drop the stray border
- Make the MCP Servers section header plain text instead of a link
- Remove a stray .orig backup file

* studio/frontend: restore Compare entry point in the sidebar

The chat-projects sidebar redesign dropped the Compare nav item and moved
it to thread-sidebar.tsx, which is not imported or rendered anywhere. That
left no way for a user to start a new model comparison (enterCompare only
fired from the guided tour and the training handoff), and broke the
Compare/Recipes/Export UI smoke test that clicks [data-tour="chat-compare"].

Re-add the Compare NavItem to the New Chat / Search group, carrying
data-tour="chat-compare" and the same new-comparison navigation as before.

* studio/frontend: use Unsloth green for the fallback profile avatar

Switch the initials-avatar background from blue to #14b789 so the sidebar
and edit-profile avatar match the Unsloth brand colour.

* studio/frontend: turn project breadcrumb into a project switcher dropdown

* studio/frontend: stop project card kebab clicks from opening the project

* studio/frontend: hide project switcher outside projects

* studio/frontend: stabilize project switcher loading

* style: project switcher alignment

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: shimmyshimmer <107991372+shimmyshimmer@users.noreply.github.com>
Co-authored-by: Unsloth <michaelhan@Michaels-MacBook-Pro.local>
Co-authored-by: Roland Tannous <rolandtannous@gravityq.ai>
Co-authored-by: Roland Tannous <115670425+rolandtannous@users.noreply.github.com>