Polish pane split drag and drop

[RA1NCS]

Summary

• Adds pane-aware split previews for file-tree drags and internal tab drags.
• Routes file-tree drops and tab drops through the same 3x3 pane-zone resolver: edge thirds split, center moves or opens without splitting.
• Makes the resolver choose the pane physically under the pointer, so drag previews do not stick to the source pane when the drag overlay is above another pane.
• Keeps the split preview scoped to the editor surface so it never covers the tab bar.
• Supports Escape during drag: first Escape suppresses split and forces center, second quick Escape aborts the drag.
• Cleans up redundant drag paths, dead hover/debug plumbing, duplicated split-zone logic, and the no-op drag hint component.

Details

• File-tree drag remains raw mouse-event based and publishes window.__fileDragData for pane drops.
• Tab drag remains dnd-kit based and publishes internal tab drag data for cross-pane movement and splitting.
• Both paths resolve their current drop target through resolveDropTarget, which checks the element stack plus viewport containment so fixed drag previews do not steal the target pane.
• Split direction and placement now come from one helper, keeping file drops, tab drops, and sidebar-resource drops aligned.
• Overlay styling uses theme accent variables instead of hardcoded accent RGB values.

Validation

• bun run typecheck
• bunx vp lint src/features/tabs/utils/internal-tab-drag.ts src/features/tabs/components/tab-bar.tsx src/features/panes/components/pane-container.tsx src/features/panes/components/split-drop-overlay.tsx src/features/file-explorer/hooks/use-file-explorer-drag-drop.ts src/features/layout/components/main-layout.tsx
• git diff --check
• Manual split testing confirmed by local app smoke test: file-tree split drag, tab cross-pane split drag, overlay placement, and Escape modifier behavior.

[mehmetozguldev]

Thanks, the shared pane-zone resolver and scoped overlay direction look good. I checked this on current master: merge is clean, typecheck passes, and the targeted
pane/tab tests plus lint pass.

One blocker before merging: the new Escape behavior is not applied to terminal tab drags. TabBar uses isDragAborted() and applyDropZoneGates(), but terminal- tab-bar.tsx still resolves the raw target zone and splits directly. That means Escape can show/suppress the hover state but terminal drops can still split, and the
double-Escape abort path can still detach the terminal.

Please route terminal tab drag end through the same drag gates/split config helpers as editor tab drag, or explicitly scope the Escape behavior away from terminal
drags.

[RA1NCS]

Addressed review. Terminal tab drag end now goes through the same drag-gate and split-config helpers as editor tab drags, so single-Escape suppression and double-Escape abort both apply before split/drop handling.