Fixes #93901

TS 3.9 is smarter about catching cases where an if statement is always true. This revealed a few places in our codebase where we were checking to see if a function property exists before calling it, but the property is not nullable

* Fix #93691

* Fix #93961

Fixes #91336

Also adds `timeline.pageSize` to explicitly choose a page size

fixes #94828

Fix #93885

This happened because the first terminal tab got created but since the element didn't exist
yet it wasn't marked as hidden, which caused the actual active terminal to be pushed below it.

Fixes #94714

#94677

#95032

fixes #94137

#94677

Support validated regex-based link detection and word-based as a fallback that uses quick access