Expand medical abbreviations in text.

Recognizes common medical abbreviations like:

• DM2 → diabetes mellitus type 2
• w/ → with
• CKD → chronic kidney disease
• HTN → hypertension
• CHF → congestive heart failure
• COPD → chronic obstructive pulmonary disease

Also provides hints for alphabetic index navigation (main_term_hint, subterm_hints) which are useful for subsequent code lookups.

Example:

{"text": "DM2 w/ CKD stage 3"}

Response:

{
  "expanded_text": "diabetes mellitus type 2 with chronic kidney disease stage 3",
  "expansions": [
    {"original": "DM2", "expanded": "diabetes mellitus type 2", ...},
    {"original": "w/", "expanded": "with", ...},
    {"original": "CKD", "expanded": "chronic kidney disease", ...}
  ]
}

Free-tier keys are limited to 500 characters of input; Pro and Enterprise keys may send the full 10,000. Over the limit returns 413. This endpoint normalizes shorthand before an index lookup — it is not intended for whole clinical notes.