chore: bump pro submodule to main after #18 merge (d5d3460d)

Point the pro submodule at pro-main's merge commit for #18 (streaming-TTS STOP +
estimateClipDuration) instead of the pre-merge branch tip, so #498 references a commit
that lives on pro/main.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: alichherawalla