Adds packages/core/src/index.ts as the convenience re-export barrel for
all Dialog parts, Presence, Portal, VisuallyHidden, createFocusTrap,
createScrollLock, and createDismiss. Also resolves pre-existing biome
formatter and noNonNullAssertion violations across five files so CI passes.
Implements DialogRoot, Content, Title, Description, Trigger, Close, Portal, and Overlay parts with full context wiring, focus trap, scroll lock, and dismiss. Also fixes pre-existing TS6 exactOptionalPropertyTypes errors in create-disclosure-state and presence, and silences TS6.0 deprecation warnings via ignoreDeprecations.
