Fix spoiler animation overlay and wrapped-line clipping

[Bharathboy1]

Canvas positioning and DOM management:

• Particle canvases are now positioned relative to the SpoilerSpan container rather than absolutely on the page, ensuring correct alignment regardless of page scroll or layout changes. All calculations for canvas placement and bounding boxes have been updated to use the container's coordinates. [1] [2] [3] [4] [5]
• Canvases are now appended to the container div instead of the document body, keeping the DOM cleaner and encapsulating the effect within the component. [1] [2]

TypeScript and code quality improvements:

• Added non-null assertions (!) to various class properties (such as el, slotElement, containerDiv, etc.) to satisfy TypeScript strict property initialization checks. [1] [2]
• Improved the type assertion for the container div reference in the JSX render method.

Styling improvements:

• Added overflow: hidden to the container's CSS to prevent particle effects from spilling outside the spoiler span.
  Improved bounding-box measurement so the effect tracks actual text fragments rather than treating wrapper elements as a full block.
  Updated canvas repositioning logic to stay aligned with the spoiler text during scroll and layout updates.
  Added overflow: hidden to the spoiler host so the effect is clipped to the spoiler’s own inline area.

Note: This is ai fix