[Diwaspant132]

fix(ui-elements): center tooltip alignment, add text crash guard, and fix ActionButton icon overflow

Description

This pull request addresses several UI alignment, reliability, and accessibility defects across @embeddedchat/ui-elements:

1. Tooltip Centering (left: 50%): In Tooltip.styles.js, tooltips previously used a hardcoded left: 64%; transform: translateX(-50%), causing every tooltip in the chat interface to be skewed ~14% off-center to the right of its anchor button. Changed to left: 50%; transform: translateX(-50%) to ensure exact centering.
2. Defensive Text Guard & Crash Prevention: Tooltip.js previously executed {text.charAt(0).toUpperCase() + text.slice(1)} without verifying that text was a defined non-empty string. Hovering over elements without a title (e.g. attachments with falsy attachment?.title) threw an unhandled TypeError: Cannot read properties of undefined (reading 'charAt'). Added safe string handling and only render the tooltip popup when hasText is true.
3. Timer Memory Leak Fix: Replaced functional-component-scoped let touchTimer with useRef and added unmount cleanup in useEffect.
4. Keyboard Accessibility (a11y): Added onFocus, onBlur, and Escape key dismissal handlers along with role="tooltip" and aria-hidden attributes so keyboard users navigating with Tab can access tooltips.
5. Arrow Normalization on "down": Handled both position="bottom" and position="down" variants so arrows invert (rotate(180deg)) and anchor properly when "down" is passed (e.g. in AttachmentMetadata.js).
6. ActionButton Small/Large Icon Sizing: When size="small" was passed to ActionButton (a 20px / 1.25rem square button), icons defaulted to 24px (1.5rem), overflowing outside the button bounds. Added getIconSize helper that derives appropriate icon sizing based on button size (small -> 1rem, large -> 1.75rem, medium -> 1.25rem) while supporting explicit string and object overrides.

Acceptance Criteria fulfillment

• Tooltip container is centered over anchor elements (left: 50%).
• Tooltip safely handles undefined, null, and empty strings without runtime errors.
• Keyboard focus (onFocus / onBlur) and Escape key dismissal supported.
• role="tooltip" and aria-hidden attributes added.
• size="small" ActionButton displays properly scaled 1rem icon without container overflow.
• 19 unit tests added and passing.
• Prettier and ESLint pass without warnings or errors.

PR Test Details

• Run unit test suites: node --test packages/ui-elements/src/components/**/*.test.mjs (19/19 passing).
• Run formatting check: yarn format:check (10/10 projects passed).
• Verify in Storybook: cd packages/ui-elements && yarn storybook -> Components -> Tooltip & ActionButton.