Clean up UI spacing/fallbacks in Durable Column Header

Summary: Correct minor spacing issues, makes long Conpherence Titles fallback to ellipsis when overflow. Fixes T7541

Test Plan:
Test a long and short title Conpherence.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7541

Differential Revision: https://secure.phabricator.com/D12048