fix(react-list): fix useList and useListItem as prop handling

[dmytrokirpa]

Summary

Companion to #35821. Isolates the hook-level test additions as a master-passing baseline, plus fixes an operator precedence bug that would have silently broken the as prop when props.as is explicitly set.

• Commit 1 — fixes operator precedence in useList_unstable and useListItem_unstable: props.as || navigationMode === 'composite' ? 'div' : DEFAULT_ROOT_EL_TYPE was parsed as (props.as || navigationMode === 'composite') ? 'div' : DEFAULT_ROOT_EL_TYPE, meaning a truthy props.as always resolved to 'div'.
• Commit 2 — adds baseline tests for useList_unstable and useListItem_unstable:
  • Default state: role, root element, no selection
  • Selection mode: listbox/option roles, toggle via Space key, onSelectionChange callback
  • Composite navigation mode: div root, grid/row roles
  • Explicit as prop override (also serves as a regression test for the precedence fix)

Why

These tests are useful independent of #35821 — they pin existing behavior so that the refactor in #35821 (which introduces useListBase_unstable and useListItemBase_unstable and delegates the original hooks to them) produces a reviewable diff. Any assertion that needs updating there surfaces a behavior change worth discussing.

🤖 Generated with Claude Code

[github-actions]

📊 Bundle size report

Package & Exports	Baseline (minified/GZIP)	PR	Change
react-components react-components: entire library	1.3 MB 325.038 kB	1.301 MB 325.039 kB	4 B 1 B
react-list List	87.128 kB 25.767 kB	87.13 kB 25.767 kB	2 B
react-list ListItem	111.036 kB 32.683 kB	111.038 kB 32.684 kB	2 B 1 B

Unchanged fixtures

Package & Exports	Size (minified/GZIP)
react-components react-components: Button, FluentProvider & webLightTheme	70.415 kB 19.963 kB
react-components react-components: Accordion, Button, FluentProvider, Image, Menu, Popover	237.205 kB 68.894 kB
react-components react-components: FluentProvider & webLightTheme	43.63 kB 14.026 kB
react-portal-compat PortalCompatProvider	8.386 kB 2.624 kB
react-timepicker-compat TimePicker	108.995 kB 36.042 kB

_{🤖 This report was generated against 70972f1b1169ae00247b080202ce05581c2dd62f}

[github-actions]

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