fix(activity): keep tooltips within viewport (@ahamSel)

[ahamSel]

Description

Activity-calendar tooltips could be clipped when their trigger day was close to either viewport edge, particularly on small screens.

This update measures each tooltip when it is shown and shifts only the tooltip box far enough to keep it inside an 8 px viewport margin. The arrow stays centered over the hovered day. Tooltip text also scales modestly on narrow viewports and wraps when needed.

Only opacity and transform animate, preventing responsive tooltip sizing from starting animations for every calendar day during resize.

Closes #8240

[fehmer]

hi @ahamSel , thank you for your contribution.

The problem still exists for tooltips close to the edge on small screens on both sides:

[ahamSel]

Thanks for pointing this out. I replaced the final-week alignment with viewport-edge detection on both sides. The tooltip box now shifts inward only when needed while its arrow stays centered over the hovered day; the text also scales modestly and wraps on narrow screens. I verified the behavior manually at small viewport widths.

[Miodec]

Screen.Recording.2026-08-14.at.12.53.19.mov

Something expensive is running on resize because its very slow.

[ahamSel]

Thanks for catching this. The tooltip library's transition: all was animating the responsive font size, padding, and max-width on every day, even when its tooltip was hidden. Resizing the profile triggered 2,184 of those transitions across 364 days.

I limited the tooltip transitions to opacity and transform. The sizing transitions are now gone, while the tooltip fade, edge positioning, and centered arrow remain. I checked the left, middle, and right tooltips at narrow and wide viewport widths and ran the existing calendar tests (29 passed), formatting, and lint checks. Also rebased onto current master.

I also tested by dragging the browser window narrower and wider, and resizing now feels smooth.