Tabs strip and Directory list: small fixes

Seen during the visual check for Task 7210 (project side pane, 1024px and 1280px windows). 1. `components/Tabs.tsx`: a scrollable strip whose labels shrink after first render (a count landing, a label shortened) keeps MUI's end chevron from the first overflow even though everything now fits. Make the strip re-measure its scroll buttons when its labels change, so callers don't have to key-remount it (as `ProjectMergeLaneTab` does now). 2. Directory › Projects list at a 1024px window: project names get cut ("org-a-pro…", "org-b-probe-…") while the org chip keeps its full width. Let the name win: shorten or drop the chip on a narrow list, or show the whole name on hover. Out of scope: the merge lane tab itself (Task 7210), the Tabs wrap/overflowMenu modes. Done means: - Each item is fixed and covered by a web test, or declined with a reason, and checked visually at 1024px.

Tabs drops stale scroll chevrons once labels fit; Projects list keeps names whole at 1024px (org chip leaves the line instead). Covered by web + e2e tests, checked at 1024px, quick gate green, PR #5892 merged as 4002b24a6. Follow-ups: draft #7240.