fix(react): flip Select caret when content collides above trigger

[midego1]

Problem

On long Select lists (e.g. Artifacts → GSC board site picker), the shared Select looks correct when a top item is selected (menu opens below the trigger).

When a bottom item is selected, the menu flips above the trigger, but:

1. The decorative caret stays on the top edge pointing up (wrong edge / wrong direction for data-side=top).
2. The open menu feels disconnected from the trigger — item-aligned positioning leaves the selected row stranded at the far end of a floating panel.

Expected

• data-side=bottom: caret on the top edge of the menu, pointing toward the trigger.
• data-side=top: caret on the bottom edge of the menu, pointing toward the trigger.
• Selected / nearby rows stay visually close to the trigger for long lists.

Screenshots (redacted)

Top item selected — menu below, caret on top edge (OK):

Bottom item selected — menu above, caret still on top edge (bug):

Close-up of flipped menu + wrong caret:

Fix

In packages/react/src/components/select.tsx:

• Default SelectContent to Radix position="popper" with sideOffset / collisionPadding so the panel stays anchored to the trigger when it flips.
• Render SelectPrimitive.Arrow (popper-only) so the caret follows data-side.
• Move scroll overflow onto the viewport so the arrow is not clipped.

Scoped to the shared Select primitive only — no GSC artifact business-logic changes.

Test plan

• Open a long Select (many options); select a top item → menu below, caret on top edge toward trigger.
• Select a bottom item near the viewport edge → menu above, caret on bottom edge toward trigger.
• Confirm selected row stays near the trigger (not stranded at the far end of the panel).
• Spot-check existing Select call sites (policies, connection owner, org invite).

No dedicated Select unit/story suite in-repo; verified via packages/react typecheck after the change.

Issue

Could not create a tracking issue on UsefulSoftwareCo/executor (GitHub API 403 — token cannot open issues there). Problem section above is the bug description.