One class per provider (TwelveData, Oanda, Tiingo), all subclassing
BaseDataProvider which owns cache, validation/cleaning, freshness +
boundary guarantees, fetch_range pagination, and streaming stubs —
subclasses implement only _fetch_raw. config.json data_providers.active
selects the live feed; data_provider.py / oanda_provider.py stay as
back-compat shims. Module 16 provider-abstraction tests (253 total green).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Mc7XKYyPySVXiUpcN82QEK
Ported from feature/eurusd-support: PAIR_PRODUCERS registry with
make_config() factories per pair. xauusd.make_config is a pure
PlatformConfig-defaults wrapper (equality with the inline construction
is enforced by test); eurusd.make_config carries the donor branch's
regime weights and gates as a pre-realism baseline.
Adds 4 registry tests. 154/154 pass.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>