docs(material/form-field): update form-field prefix suffix a11y docs (#33680)

Updates Form Field components' documentation on accessibility when using
matTextPrefix and matTextSuffix by recommending usage of aria-label or
aria-describedby to ensure full context is provided for screen readers.

Fixes b/517657863

Author: essjay05

src/material/form-field/form-field.md

@@ -144,6 +144,18 @@ adds these elements' IDs to the control's `aria-describedby` attribute. Addition
 applies `aria-live="polite"` by default such that assistive technology will announce errors when
 they appear.
 
+When using static text prefixes or suffixes (such as currency symbols like `$` or unit suffixes like
+`.00` or `kg`), screen readers may not announce them as part of the input value, and some mobile screen
+readers, especially on Android/TalkBack, may expose them as separate focus stops. This can lead to
+redundant announcements or unexpected focus behavior when navigating the field.
+
+If the prefix or suffix provides important context, add an `aria-label` to the input or include the full
+meaning in `aria-describedby` so the accessible name/description matches the visible content. For example,
+if the prefix is `$` and the suffix is `.00` to indicate dollars with no cents, an appropriate `aria-label`
+could be `aria-label="Amount in dollars with 0 cents"`. When the static text is purely decorative and the
+input already conveys the full context, add `aria-hidden="true"` to the static `matTextPrefix` or
+`matTextSuffix` elements so they are skipped during swipe navigation and do not create redundant focus stops.
+
 ### Troubleshooting
 
 #### Error: A hint was already declared for align="..."