fix(ai-credits-widget): compact G$ amounts from 1K, keep history and minimums exact (#<issue>)

[blueogin]

Description

Large G$ amounts in the summary card currently show as whole numbers (21,190.79 G$), which crowds the narrower layout. As agreed with Rael and Meri, G$ amounts now compact from 1,000 up, while the History tab and vault minimums keep exact amounts. All formatting still lives in one rule in format.ts.

Where	21,190.79 G$ renders as
Summary card (Deposited, Monthly Streaming)	21.2K G$ (exact amount in tooltip)
G$ balance in the hero / amount picker	21.2K
History entries and range total	21,190.79 G$
Vault minimums	exact, still rounded up (1,549, not 1.5K)
Amounts under 1,000 are unchanged (950.5 G$). US$ formatting is unchanged.

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