Good First Issue: Add a deterministic funding-rate adapter fixture

[squaeragent]

Add a deterministic funding-rate market-data fixture under examples/ so contributors can model non-price venue data without using network access, exchange credentials, or live accounts.

Acceptance:

• The fixture is local and synthetic.
• The adapter exposes funding-rate rows in chronological order.
• The example requires no secrets, network access, wallet material, or live mode.
• Tests or a smoke command cover unknown symbol, positive limit validation, and latest funding lookup.

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Seeded from docs/launch-issues.md. Keep scope small and paper-safe.

[txhno]

ive fixed it here: #33