fix: keep SuperPins from covering tabs after the sidebar is hidden

[cmcejas]

Summary

• SuperPins' pin grid could collapse after you hide the sidebar and open it again
• regular tabs then slide up and cover the pins
• this keeps the pin section sized to its content, only uses the expanded grid while the sidebar is open, and relayouts after hide/show

Why

When the sidebar goes to 0 width, the auto-fit pin grid can lose its height. The pin icons still paint, and the normal tabs start at the top of the list. Stay-at-top's old flex: 0 1 0 made that easier to stick.

Validation

• bun run build
• prettier on the SuperPins files
• layout harness: forced the 0-height overlap (64px covering the pins), then the 1.7.3 rules recovered it (overlap 0)
• still worth a quick hide/show in Zen with the grid layout on