[material-ui][Input] Add missing InputBase class keys

[tianrking]

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Fixes #20706.

inputClasses already exposes the class keys inherited from InputBase at runtime, but InputClasses omitted adornedStart, adornedEnd, hiddenLabel, and readOnly. As a result, TypeScript rejected these valid keys when they were passed to the Input component's classes prop.

This change aligns the public type and generated API documentation with the existing runtime class map, and adds focused compile-time coverage for all four keys.

Tests:

• pnpm -F @mui/material typescript
• pnpm test:node Input (214 passed, 39 skipped)
• pnpm prettier
• pnpm eslint
• pnpm proptypes
• pnpm docs:api

[code-infra-dashboard]

Deploy preview

https://deploy-preview-48940--material-ui.netlify.app/

Bundle size

Bundle	Parsed size	Gzip size
@mui/material	0B(0.00%)	0B(0.00%)
@mui/lab	0B(0.00%)	0B(0.00%)
@mui/private-theming	0B(0.00%)	0B(0.00%)
@mui/system	0B(0.00%)	0B(0.00%)
@mui/utils	0B(0.00%)	0B(0.00%)

Details of bundle changes

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[chatgpt-codex-connector]

Emit the documented Input state classes

When endAdornment, startAdornment, or hiddenLabel is active, Input.useUtilityClasses does not compose these state slots, and inputClasses inherits their values from inputBaseClasses; the rendered classes are therefore MuiInputBase-adornedEnd, MuiInputBase-adornedStart, and MuiInputBase-hiddenLabel. The newly documented .MuiInput-* selectors never match, so users following the CSS API cannot style these states. Either compose the corresponding MuiInput classes at runtime or document the actual inherited class names.

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