fix: preserve drag text set by consumers

[nrps9909]

Summary

• initialize the Firefox text/plain drag fallback before invoking the consumer callback
• allow onDragStart consumers to set or override the drag text payload
• add a regression test for the call order and final DataTransfer value

Fixes #931.

Why

The Firefox fallback is still required, but applying it after the consumer callback overwrote any text/plain value set by the consumer. Initializing it first preserves the fallback while allowing the public callback to provide the actual payload.

Verification

• exact-base regression failed before the fix: the custom value was followed by an empty fallback
• TreeDraggable.spec.tsx: 37/37 tests passed
• full suite: 14 suites, 225 tests, and 42 snapshots passed
• TypeScript check passed
• lint passed with 0 errors (11 existing warnings)
• compile passed for ESM, CJS, declarations, and CSS
• Prettier check passed for changed files
• git diff --check passed

AI assistance disclosure: Codex was used to trace the drag-start flow, implement the focused fix, add the regression test, and run verification. The behavior and test results above were verified in this branch.

Summary by CodeRabbit

• Bug 修复
  • 修复节点拖拽时自定义拖拽数据可能被默认逻辑覆盖的问题。
  • 现在可正确保留并读取自定义的 text/plain 拖拽内容。

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: f40bce00-e9ec-4824-9ee7-6c9b83f63e4d

📥 Commits

Reviewing files that changed from the base of the PR and between 2492cbc and 1b87df9.

📒 Files selected for processing (2)

• src/TreeNode.tsx
• tests/TreeDraggable.spec.tsx

Included review availability: Your plan provides up to 4 included reviews per hour; 3 remain after this review.

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Walkthrough

Tree 的拖拽开始流程先写入默认 text/plain 数据，再调用用户回调。新增测试验证用户设置的自定义拖拽数据不会被覆盖。

Changes

拖拽数据顺序

Layer / File(s)	Summary
拖拽开始数据初始化与验证 src/TreeNode.tsx, tests/TreeDraggable.spec.tsx	onDragStart 先设置拖拽数据，再调用 context.onNodeDragStart。测试确认自定义 text/plain 数据仍可通过 dataTransfer.getData 读取。

Estimated code review effort: 2 (简单) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 1b87d

The change initializes the Firefox drag-text fallback before the consumer callback so consumer-provided text is preserved, with focused regression coverage and all reported checks passing; no actionable merge-blocking risk remains.

Suggested reviewers: emilyyyliu

Poem

小兔先写拖拽字，
回调随后稳稳至。
自定义数据不迷路，
测试轻敲确认时。
树影摇摇风里舞。

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	标题准确描述了主要变更：保留消费者设置的拖拽文本。标题简洁、明确，并与代码和测试变更一致。
Linked Issues check	✅ Passed	PR 将 Firefox 的 text/plain 回退数据设置移到 context.onNodeDragStart 之前，使消费者可以设置或覆盖拖拽文本。新增回归测试验证了回调顺序和最终 DataTransfer 值，满足 Issue #931 的编码目标。
Out of Scope Changes check	✅ Passed	代码变更仅调整 onDragStart 的执行顺序，并新增相关回归测试。所有变更都直接支持 Issue #931 和 PR 目标，未发现无关或超出范围的修改。
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2…

Full details: Docstring Coverage

Explanation

No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2 files.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.84%. Comparing base (2492cbc) to head (1b87df9).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1071   +/-   ##
=======================================
  Coverage   99.84%   99.84%           
=======================================
  Files          15       15           
  Lines        1319     1319           
  Branches      400      400           
=======================================
  Hits         1317     1317           
  Misses          2        2           

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