fix(tooltip): complete behavior and accessibility

[tbielich]

Summary

• add configurable tooltip show delay
• add placement-aware arrow rendering
• generate or accept a stable tooltip ID
• connect the trigger through aria-describedby
• synchronize aria-hidden for hover, focus, blur, and Escape
• update macro and documentation
• add contract-level unit coverage

Issue

Closes #35

Boundaries

• no Table changes
• no Popover behavior
• tooltip content remains non-interactive

Validation

• all four placements retain support
• default delay is 300 ms and can be overridden
• trigger receives aria-describedby
• tooltip exposes role="tooltip" and synchronized aria-hidden
• Arrow, delay, macro, and accessibility contracts are covered by tests