admin: associate inline field errors with their inputs

network assignment rows, activity filters, and the settings password pair now mark the offending input with aria-invalid and point it at the error text with aria-describedby. the prefix validator returns the row and field it is about, and any row mutation clears a message that named a position. settings numeric fields carry aria-invalid on an unparseable value.

admin/src/features/configuration/SettingsForm.tsx

@@ -13,6 +13,9 @@ import { styles as config } from "./styles";
 
 const DARK = "@media (prefers-color-scheme: dark)";
 
+/** The form is rendered once per page, so the message can hold a fixed id. */
+const MISMATCH_ID = "web.password_mismatch";
+
 const styles = stylex.create({
 	form: {
 		marginTop: "1rem",
@@ -175,12 +178,15 @@ function FieldRow({
 	}
 	if (def.kind === "number") {
 		const numeric = value as number;
+		// An empty or unparseable number reads back as NaN. The form already refuses
+		// to submit on it; this is what says so to a screen reader.
 		return (
 			<div {...stylex.props(styles.field)}>
 				<FieldLabel id={id} text={def.key} restart={restart} />
 				<input
 					id={id}
 					type="number"
+					aria-invalid={Number.isNaN(numeric) || undefined}
 					value={Number.isNaN(numeric) ? "" : numeric}
 					onChange={(e) => onChange(e.target.valueAsNumber)}
 					{...stylex.props(styles.fieldInput, shared.focusRing)}
@@ -286,6 +292,8 @@ export default function SettingsForm({ envelope }: { envelope: SettingsEnvelope
 											id="web.password"
 											type="password"
 											autoComplete="new-password"
+											aria-invalid={passwordsMismatch || undefined}
+											aria-describedby={passwordsMismatch ? MISMATCH_ID : undefined}
 											value={password}
 											onChange={(e) => setPassword(e.target.value)}
 											{...stylex.props(styles.fieldInput, shared.focusRing)}
@@ -299,6 +307,8 @@ export default function SettingsForm({ envelope }: { envelope: SettingsEnvelope
 											id="web.password_confirm"
 											type="password"
 											autoComplete="new-password"
+											aria-invalid={passwordsMismatch || undefined}
+											aria-describedby={passwordsMismatch ? MISMATCH_ID : undefined}
 											value={confirm}
 											onChange={(e) => setConfirm(e.target.value)}
 											{...stylex.props(styles.fieldInput, shared.focusRing)}
@@ -311,7 +321,7 @@ export default function SettingsForm({ envelope }: { envelope: SettingsEnvelope
 										</p>
 									)}
 									{passwordsMismatch && (
-										<p {...stylex.props(styles.spanRow, styles.mismatchNotice)}>
+										<p id={MISMATCH_ID} {...stylex.props(styles.spanRow, styles.mismatchNotice)}>
 											Passwords do not match.
 										</p>
 									)}