[composite] Always skip natively disabled items during list navigation

[atomiks]

isListIndexDisabled let a disabledIndices override mark natively disabled elements as enabled. Tabs.List passes an empty disabledIndices so that disabled tabs stay focusable, but that also applied to elements carrying a native disabled attribute, e.g. <Tabs.Tab render={<button disabled />} />. The composite moved its active index onto such a tab and the focus() call silently failed, leaving keyboard navigation stuck: pressing ArrowRight from tab A focused A again, and only the next press reached C.

Natively disabled elements can never receive focus, so isListIndexDisabled now always skips them, regardless of disabledIndices. aria-disabled items are unaffected and remain focusable while disabled (the APG default). Menu and Select pass the same override, so the same applies there; tests cover Tabs and Menu. This also means both APG conventions are now reachable: the disabled prop keeps an item in the focus order, while rendering a natively disabled element removes it.

Closes #5132

[pkg-pr-new]

• base-ui-tanstack-start

• vite-css-base-ui-example

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/react@5185
  

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/utils@5185
  

commit: c2cb668

[code-infra-dashboard]

Bundle size

Bundle	Parsed size	Gzip size
@base-ui/react	🔺+51B(+0.01%)	🔺+19B(+0.01%)

Details of bundle changes

Performance

Total duration: 990.04 ms +150.60 ms^(+17.9%) | Renders: 78 ⁽⁺⁰⁾

Test	Duration	Renders
Tabs mount (200 instances)	189.29 ms 🔺+44.60 ms(+30.8%)	4 (+0)
Popover mount (300 instances)	71.18 ms 🔺+25.04 ms(+54.3%)	1 (+0)
Combobox type — 500 items, all stay mounted (type "Row ")	30.46 ms 🔺+11.29 ms(+58.9%)	11 (+0)
Tooltip mount (300 contained roots)	43.50 ms 🔺+10.61 ms(+32.2%)	1 (+0)
Dialog mount (300 instances)	48.92 ms 🔺+9.23 ms(+23.2%)	1 (+0)

…and 1 more (+8 within noise) — details

Metric alarms

Test	Metric	Change
Tabs mount (200 instances)	bench:paint	🔺 +85.22 ms
Popover mount (300 instances)	bench:paint	🔺 +37.53 ms
Combobox type — 500 items, all stay mounted (type "Row ")	bench:paint#combobox-open	🔺 +24.21 ms
Combobox type — 500 items, all stay mounted (type "Row ")	bench:paint	🔺 +24.21 ms
Tooltip mount (300 contained roots)	bench:paint	🔺 +14.28 ms
Dialog mount (300 instances)	bench:paint	🔺 +15.34 ms
Combobox type — 500 items, narrows to ~11 (type "Row 25")	bench:paint#combobox-open	🔺 +12.02 ms
Combobox type — 500 items, narrows to ~11 (type "Row 25")	bench:paint	🔺 +12.02 ms

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