fix: restore tab drag-and-drop pane splitting

[gnoviawan]

Summary

• Disabled Tauri's native dragDropEnabled so HTML5 DnD events reach the WebView2 DOM on Windows
• Reunified split PaneDndProvider into a single instance wrapping both PaneRenderer and FileExplorer, restoring shared isDragging state
• Added onDragOver handler to tab bar container to prevent no-drop cursor in gaps between tabs

Root Cause

Three separate issues combined to break tab drag-and-drop:

1. Tauri intercept: dragDropEnabled defaults to true, which blocks all HTML5 drag events at the native level
2. Split provider (PR feat: codex inspired dark theme ui redesign with layout fixes #75 regression): Two separate PaneDndProvider instances meant isDragging set in one was invisible to the other
3. Missing handler: Tab bar container lacked onDragOver, causing no-drop cursor between tabs

Test plan

• Drag a tab from one pane to another pane's content area — DropZoneOverlay appears with split zones
• Drop on a zone (left/right/top/bottom) — tab moves to new split pane
• Drop on center zone — tab moves to target pane
• Drag tab across tab bar gaps — cursor shows move indicator, never no-drop
• Tab reorder within same pane still works
• File explorer drag to pane shows DropZoneOverlay
• Drag cancel (Escape / drop outside) resets cleanly

🤖 Generated with Claude Code

Summary by CodeRabbit

Release Notes

• New Features

  • Improved drag-and-drop handling in the workspace interface.
  • Enhanced empty state screen with better visual presentation and a "Create Your First Project" button for easier project creation.

• Chores

  • Updated workspace configuration for improved stability.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 819f7ba0-853c-4025-bf0f-d34b3b9ac171

📥 Commits

Reviewing files that changed from the base of the PR and between f66cf47 and 199a2d5.

📒 Files selected for processing (3)

• src-tauri/tauri.conf.json
• src/renderer/components/workspace/WorkspaceTabBar.tsx
• src/renderer/layouts/WorkspaceLayout.tsx

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📝 Walkthrough

Walkthrough

Introduces drag-and-drop infrastructure for the workspace. Disables OS-level drag-drop in Tauri config, adds drag-over handler to tab bar, wraps layout in PaneDndProvider, and enhances the empty state with improved UI components.

Changes

Cohort / File(s)	Summary
Tauri Configuration src-tauri/tauri.conf.json	Added dragDropEnabled: false to Windows main configuration to control OS-level drag-and-drop behavior.
Tab Bar Drag Handling src/renderer/components/workspace/WorkspaceTabBar.tsx	Added onDragOver handler to top-level container div to prevent default drag-over behavior and set dropEffect to 'move'.
Layout Restructuring & Empty State src/renderer/layouts/WorkspaceLayout.tsx	Wrapped main layout in PaneDndProvider, reorganized conditional rendering around content sections, and redesigned the No Projects empty state with icon, heading, description, and action button.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• fix: consolidate tab drag-and-drop to native HTML5 API #74: Consolidates tab drag-and-drop and PaneDndProvider setup changes that directly overlap with this PR's drag-and-drop infrastructure additions and provider boundary modifications.

Suggested labels

phase-1

Poem

🐰 With whiskers twitching, I hop with glee,
Dragging, dropping, wild and free!
Tabs now glide through panes divine,
Configuration set—the workspace shines! ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix: restore tab drag-and-drop pane splitting' directly describes the primary change: restoring drag-and-drop functionality for tab pane splitting. It aligns with all three key changes: disabling Tauri's dragDropEnabled, reunifying PaneDndProvider, and adding the onDragOver handler.

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✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch worktree-fix-tab-dnd-pane-splitting

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