fix(Groups): prevent stale state from overwriting group drag position

[draedful]

Summary

• Fixed a bug where groups drag much slower than blocks (or appear stuck)
• Root cause: subscribeToGroup was using this.state (stale) instead of this.getState() (pending) when suppressing rect updates during drag

What changed and why

During group drag, the flow is:

1. handleDrag() calls setState({ rect: newPos }) → stores new rect in data.nextState (but this.state is NOT updated until the render cycle)
2. onDragUpdate moves the contained blocks
3. Block position signals fire synchronously, triggering subscribeToGroup
4. With isDragging=true, the handler calls setState({ ...this.state, ...groupWithoutRect })

The bug: this.state.rect is the stale original position. Since data.nextState already exists from step 1, setState hits the else branch and does assign(data.nextState, { rect: stalePos, ... }), overwriting the correct rect set by handleDrag back to the initial position. This repeats every frame, making the group appear stuck.

Fix: Replace this.state with this.getState() which returns data.nextState when a pending state update exists, preserving the correct rect from handleDrag.

Files changed

• src/components/canvas/groups/Group.ts — one-line fix in subscribeToGroup

🤖 Generated with Claude Code

Summary by Sourcery

Bug Fixes:

• Fix group dragging behavior where groups could appear stuck or move more slowly than blocks due to stale state overwriting the pending drag rect.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Adjusts group drag state handling so that subscription updates use the pending next state instead of stale component state, preventing group drag position from being overwritten during the same frame.

File-Level Changes

Change	Details	Files
Prevent stale group state from overwriting drag-updated rect during ongoing drags.	In the group subscription handler, when suppressing rect updates during drag, spread the result of getState() rather than this.state into the new state object. Document in comments that getState() returns the pending nextState (including the rect set by handleDrag in the same frame), avoiding overwriting the correct rect with a stale rect value.	src/components/canvas/groups/Group.ts

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[sourcery-ai]

Hey - I've left some high level feedback:

• In the dragging branch, consider avoiding spreading the entire result of getState() and groupWithoutRect into setState and instead explicitly set only the fields that need to change to reduce the risk of inadvertently overwriting unrelated state properties.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- In the dragging branch, consider avoiding spreading the entire result of `getState()` and `groupWithoutRect` into `setState` and instead explicitly set only the fields that need to change to reduce the risk of inadvertently overwriting unrelated state properties.

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