fix: prevent child nodes from disappearing in v5 by disabling parent selection

[dilipkumar6306316-art]

Background

This PR addresses a rendering regression observed in ECharts v5 when dealing with hierarchical structures (Treemap/Graph) that utilize upperLabel. Under specific interaction sequences, child nodes would intermittently disappear from the canvas.

Problem Analysis

The issue occurs when a parent node (e.g., a container like 'Blob' or 'Pool') enters the selected state while upperLabel is active. The internal state transition logic in v5 seems to conflict with the rendering of child elements during hover-in and hover-out events on a selected parent.

Key observations:

1. Visual Glitch: Selecting a parent node followed by hovering causes child nodes to lose their rendering context and vanish.
2. Style Inconsistency: The select.itemStyle.color for parent nodes incorrectly inherits borderColor instead of the specified selection color.

Proposed Solution

Since the select state logic for labeled parent containers is currently unstable, this PR introduces a safeguard by setting select: { disabled: true } for parent-level nodes. This ensures that:

                1. The visual integrity of the child nodes is preserved during all hover interactions.
                2. The rendering engine does not enter a broken state-transition loop for container nodes.

This is a non-breaking workaround that maintains the core functionality of the diagram while fixing the "disappearing nodes" bug for end-users.

Test Cases
1.Initialize a Treemap with hierarchical data and upperLabel: { show: true }.
2.Click to select a parent node.
3.Move the cursor in and out of the parent node's boundary.

Result: All child nodes remain visible.

Type of Change
Bug fix
Documentation update

Related Issue: #20098

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