fix(waterdata)!: return (df, BaseMetadata) from get_codes

[thodson-usgs]

Problem

get_codes is the only public waterdata getter that returns a bare DataFrame instead of the module-wide (DataFrame, BaseMetadata) tuple. So the universal idiom every other getter supports —

df, md = waterdata.get_codes("samplemedia")   # ValueError: too many values to unpack

— breaks, even though get_codes already builds response and calls _raise_for_non_200(response) (the metadata is in hand, just discarded).

Fix

Return (df, BaseMetadata(response)), matching get_reference_table and every other getter.

⚠️ Breaking change. Existing callers doing df = get_codes(...) must switch to df, _ = get_codes(...). Opened as a draft so maintainers can decide whether to take the break now or stage a deprecation. get_codes is a relatively new waterdata addition, so the blast radius should be small.

Verification (live API)

df, md = waterdata.get_codes("samplemedia")
# is 2-tuple: True · df non-empty: True · md.url set: True · md.query_time present: True

ruff clean.

🤖 Generated with Claude Code