Add expand and collapse all to the sidebar

[n00ki]

Description

Add a state-aware sidebar header action for expanding or collapsing every Folder at once. The shared tree hook accounts for nested and compacted Folder paths, preserves the existing workspace-scoped expansion state, and hides the action when there are no Folders.

The button follows established file-explorer behavior: it offers collapse-all whenever a visible Folder is open, otherwise it offers expand-all. Its Mingcute icon, tooltip, and accessible label always describe the next action.

Closes #270

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Documentation update

Testing

• Existing tests pass
• Added new tests for changes
• Tested manually (describe below)

Manual Testing Details:

Ran the Electron playground and verified expand-all and collapse-all with real pointer input. Confirmed nested files appear and disappear, the icon and accessible label change in both directions, local storage updates for the open Folder, and expanded state restores after a renderer reload.

Automated checks:

• pnpm --filter @hubble.md/ui test
• pnpm check
• pnpm check:react-compiler
• pnpm build:desktop

Checklist

• I discussed this change in a GitHub issue before submitting this PR
• I have run the linter, formatter, and tests to ensure my code is ready for review

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[github-actions]

Overview

Adds a sidebar header control to expand/collapse all folders via useSidebarTree, with compaction-aware folder IDs, workspace-scoped persistence, and tests for the main nested and empty cases.

Concerns

None. Expand/collapse walks the same compacted folder IDs as flattenRows, so nested chains stay consistent. Button label/icon track visible expanded state; action is hidden when there are no folders. Hook tests cover expand→collapse and the no-folder case.

Verdict

Found: 0 critical, 0 important, 0 suggestions

Approve

---

Reviewed by a Warp Factory agent.

[github-actions]

Overview

Adds a sidebar header control to expand/collapse all folders via useSidebarTree.toggleAllFolders, with compaction-aware folder IDs (all chain segments), workspace-scoped persistence, startTransition for the bulk update, and hook tests for nested expand/collapse, the empty-folder case, and compacted-chain shape changes.

Concerns

None. Expand walks the same compacted tree as flattenRows and stores every segment id, so nested and later-uncompacted chains stay consistent. Button label/icon track visible expanded state; control is hidden when there are no folders. Prior expand/collapse split was simplified to a single toggle without regressing behavior.

Pre-verdict audit

• Comments: Diff adds no doc/inline comments.
• Tests: New hook tests match existing renderTree harness style and cover the distinct paths (full toggle, no folders, compaction shape change).

Verdict

Found: 0 critical, 0 important, 0 suggestions

Approve

---

Reviewed by a Warp Factory agent.