docs: clarify SpringValues typing vs CSSProperties

[joshuaellis]

Why

#1645 reports two TypeScript errors that both still reproduce on next but are working-as-designed:

• SpringValues<T> is not structurally React.CSSProperties — each entry is a SpringValue instance, not a primitive. Typing a child component's prop as CSSProperties is too narrow.
• Strict literal unions like CSSProperties['pointerEvents'] deliberately reject SpringValue<string> so typos inside useSpring (pointerEvents: 'fooo') stay caught. The error people hit is TS widening a ternary like showMenu ? 'all' : 'none' to string at the config seam.

Loosening either type would weaken safety for everyone to paper over patterns that have clean call-site fixes. Better to document the patterns.

Changes

• Expanded the SpringValues glossary entry with subsections for child-component typing and literal-value widening.
• Added a Typing components that receive animated styles section to the Animated Elements concept page.
• Added SpringValues to the useTransition TS Glossary list (was missing).

Closes #1645

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Project	Deployment	Actions	Updated (UTC)
react-spring	Error		May 22, 2026 8:49am