fix: avoid repeated graph tooltip layout

[JJLiebig]

Summary

• Measure GraphTooltip only on mount, tooltip resize, or window resize.
• Derive collision placement from cached dimensions and move anchors with CSS translate.
• Add bounded browser regression coverage and prepare @nextide/ui 2.3.1 metadata.

Validation

• Focused GraphTooltip Chromium qualification: passed
• pnpm run check: passed
• pnpm run qualify: 19 passed
• npm pack --dry-run --access public: @nextide/ui@2.3.1
• React Doctor changed scope: 100/100
• Review Suite fast rvw_571b0abb: clean