## Summary
Fixes scroll behavior in the rich text editor.
Long content was unbounded — the popup grew off-screen, the
expand-to-side-panel button became unreachable, and the side panel
itself didn't scroll either.
Closes#20309
## Changes
- `RichTextFieldInput`: cap the popup at `min(60vh, 500px)` and wrap the
editor in a scrollable region. Collapse button stays at the top via
`align-items: flex-start`.
- `RecordInlineCellEditMode`: add `shift()` middleware to keep the popup
inside the viewport after `flip()` triggers (previously the popup could
extend above the viewport top with the collapse button out of reach).
- `SidePanelContainer` / `SidePanelRouter`: add `min-height: 0` to the
flex-column chain so the existing `overflow-y: auto` on the content area
can actually clip and scroll long children.
The previous attempt in #20310 added the same `min-height: 0` plus a
nested overflow wrapper inside the rich-text page; the nested wrapper
turned out to be the reason scrolling didn't work.
## Test plan
- [x] Open a record with a long `RICH_TEXT` field
- [x] Click the field — popup opens bounded; long content scrolls inside
- [x] Click the expand button (top-right) — side panel opens
- [x] Side panel: long content scrolls vertically
- [x] Popup near the bottom of the viewport flips upward and stays fully
inside the viewport (collapse button remains visible)
- [x] `lint:diff-with-main`, `typecheck`, prettier — green
https://github.com/user-attachments/assets/827be881-aadd-49ed-9ddc-7566c00cf4be
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Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Nick
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