fix: eliminate props divergence between CoreNode and CoreTextNode

[chiefcll]

Summary

• Fixed a bug where CoreTextNode.textProps and CoreNode.props diverged after setter calls. CoreNode's constructor was field-copying into a new this.props object, while CoreTextNode kept a reference to the original incoming props as this.textProps. After any property setter (e.g. node.color = 0xff0000ff), shared fields like color, x, y on textProps went stale.
• Removed the redundant object copy in CoreNode's constructor. resolveNodeDefaults already creates a fresh single-use object, so the second allocation was unnecessary. this.props = props directly, with the six setter-managed fields (texture, shader, src, rtt, boundsMargin, scale) destructured before being nulled in-place.
• Net reduction of ~34 lines and one fewer object allocation per node.

Test plan

• Verify text nodes reflect color changes after construction (set color via setter, confirm textProps.color matches)
• Verify texture, shader, src, rtt, boundsMargin still initialize correctly through their setters
• Run existing test suite
• Visual regression check on text rendering (both SDF and Canvas paths)

🤖 Generated with Claude Code

[chiefcll]

fixes the architectural issue of bug #1