Fix token set folder drag-reorder scrambling order when folders are expanded

[Copilot]

Dragging a folder to reorder it produced a scrambled result when folders were expanded. The bug worsened when folder structures had been modified by renaming sets into existing folders.

Root Cause

ensureFolderIsTogether used a delta-based move that only repositioned direct children (parent === value.path). Grandchildren were left in place, becoming orphaned at the top of the list.

// Before drag: [common, common/base, common/heading-color, common/heading-color/mobile, global]
// After drag (old): [global, common/heading-color/mobile, common, common/base, common/heading-color]
//                            ^^^^^ orphaned grandchild                    ^^^^^ sub-folder at wrong position
// After drag (new): [global, common, common/base, common/heading-color, common/heading-color/mobile]

Changes

• ensureFolderIsTogether: Replace delta-based child movement with a grouping approach — collect all descendants (parent === path or parent.startsWith(path + '/')), strip them from their scattered positions, and re-insert them contiguously after the folder in their original relative order.

• findOrderableTargetIndexesInTokenSetTreeList: Fix startsWith(path) → parent === path || startsWith(path + '/') to avoid falsely counting children of prefix-matching sibling folders (e.g. themes2 counted as child of themes).

• TokenSetTree handleReorder: Same startsWith boundary fix in the collapsed-folder children lookup.

[changeset-bot]

🦋 Changeset detected

Latest commit: 7dcb0a8

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@tokens-studio/figma-plugin	Patch

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[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 0 complexity . 16 duplication

Metric	Results
Complexity	0
Duplication	16

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[github-actions]

⤵️ 📦 ✨ The artifact was successfully created! Want to test it? Download it here 👀 🎁

[github-actions]

Commit SHA:ef1cbd26915901b63020f228e78e23567a09e5af

Test coverage results 🧪

Code coverage diff between base branch:main and head branch: copilot/fix-token-set-folder-drag-reordering 

Status	File	% Stmts	% Branch	% Funcs	% Lines
🟢	total	63.03 (-0.01)	54.94 (0.02)	60.12 (0)	63.34 (0)
🔴	packages/tokens-studio-for-figma/src/app/components/TokenSetTree.tsx	64.55 (0)	41.02 (-1.08)	62.06 (0)	64.7 (0)
🟢	packages/tokens-studio-for-figma/src/utils/dragDropOrder/ensureFolderIsTogether.ts	87.5 (-12.5)	75 (25)	100 (0)	90.9 (-9.1)

[github-actions]

Commit SHA:ef1cbd26915901b63020f228e78e23567a09e5af
Current PR reduces the test coverage percentage by 1 for some tests