feature: add floatingTabBehavior option for browser-style floating tab management (#1161)

[shay-dr]

Closes #1161

Adds a floatingTabBehavior option to DockviewOptions with two modes:

• "default" (or omitted): No behavior change — full backward compatibility
• "browser": Enables two features:
  • Floating-to-floating merge: Dragging a tab from one floating group onto another merges it into the target, rather than docking to the grid
  • Tear-off to float: Dragging a tab out of a multi-tab floating group creates a new floating group at the drop position, rather than docking to the grid

How it works

• In canDisplayOverlay, when the mouse is over a non-source floating group, the root drop target suppresses its overlay so the floating group's own Droptarget can handle the event
• In onDrop, when a tab is torn from a multi-tab floating group, addFloatingGroup is called instead of orthogonalize
• All changes are gated behind floatingTabBehavior === 'browser' — zero impact on default behavior

Changes

• options.ts: Add floatingTabBehavior to DockviewOptions and PROPERTY_KEYS_DOCKVIEW
• dockviewComponent.ts: Root overlay suppression + tear-off-to-float logic + _isMouseOverNonSourceFloatingGroup helper
• New test file: 11 tests covering merge, tear-off, bounds, backward compatibility, and overlay suppression

Test details

• All 752 existing tests pass unchanged
• 11 new tests cover both modes
• Manual: created two floating groups, drag tab between them with floatingTabBehavior="browser"
• Manual: verified default behavior unchanged when option is omitted

[codesandbox-ci]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

Latest deployment of this branch, based on commit 5eae784:

Sandbox	Source
dockview-app	Configuration
editor-gridview	Configuration
externaldnd-dockview	Configuration
fullwidthtab-dockview	Configuration
iframe-dockview	Configuration
keyboard-dockview	Configuration
nativeapp-dockview	Configuration
rendering-dockview	Configuration

[shay-dr]

I forgot to sign, hence my force push.

[mathuo]

Could you remove the tsBuildInfo files?

[shay-dr]

@mathuo done.