[jaygeorge]

Description of the Problem

ui/Field passed :for="props.id" to its label, but id was optional and omitted on most call sites (including login). Nested controls generated their own ids via useId(), so the label’s for pointed at nothing and the control had no accessible name.

axe-core reported critical label violations on login, password reset, and other CP screens. WCAG 2.1 SC 1.3.1 and 4.1.2.

What this PR Does

• Auto-generates a Field id when none is provided, wires it to the label’s for, and exposes a label id for aria-labelledby
• Lets the first nested control (Input, Textarea, Combobox/Select, Switch, Slider) claim that id via useUiFieldId
• Does not inject explicit Field ids (e.g. Publish’s field_*), so nested controls inside fieldtypes don’t share duplicate ids
• Puts Combobox/Select association on the trigger (id + aria-labelledby) when the search input isn’t rendered; puts Slider id on the thumb
• Adds unit coverage for association, single-claim, explicit-id isolation, and Combobox labelling

Fixes #15389

How to Reproduce

1. Visit /cp/auth/login (before this PR)
2. Inspect the Email input: id="v-0" (or similar) while the “Email” label has for=""
3. Or run axe-core and observe the label violation on both inputs

After this PR, the label’s for matches the input’s id.

[jackmcdade]

@copilot resolve the merge conflicts in this pull request

[Copilot]

@copilot resolve the merge conflicts in this pull request

Resolved the 6.x merge conflict in Switch.vue, preserving both Field id association and the newer standalone accessible-name behavior. Merge commit: $(git rev-parse --short HEAD). The focused Field/Switch tests pass.