fix: make showConnectionArrows setting properly control arrow visibility

[Antamansid]

Fix showConnectionArrows setting

Issue

The showConnectionArrows setting was defined in the configuration but wasn't actually controlling the visibility of connection arrows. Arrows were always being rendered regardless of the setting value.

Root Cause

In the BlockConnection class, the arrow was always being added to the batch renderer in the constructor and updated in the applyShape method, without checking the showConnectionArrows setting.

Additionally, there was an inconsistency between propsChanged and applyShape methods:

• propsChanged was using nextProps.showConnectionArrows to determine whether to add/remove the arrow
• applyShape was using this.props.showConnectionArrows which might contain outdated values

Changes

1. Added an arrowAddedToBatch flag to track whether the arrow is currently in the batch renderer
2. Centralized all arrow visibility logic in the applyShape method
3. Modified applyShape to accept an optional props parameter, allowing it to work with the most current props
4. Updated propsChanged to pass the new props to applyShape
5. Updated unmount to only delete the arrow if it's actually in the batch
6. Added comprehensive JSDoc comments to explain the arrow rendering logic and potential pitfalls

Testing

Verified that:

• When showConnectionArrows is true, arrows are displayed in the middle of connections
• When showConnectionArrows is false, arrows are not displayed
• When the setting is changed at runtime, arrows appear/disappear accordingly

[gravity-ui-bot]

Preview is ready.