[config] testnet.toml missing Chapel Chainlink feed address list and no startup warning when feeds absent

[obchain]

PR: #51 (feat/23-testnet-config)
File: config/testnet.toml (new), crates/charon-cli/src/main.rs line 148
Refs #51

Problem

The PR does not include a [chainlink.bnb_testnet] section in testnet.toml. This means PriceCache is constructed with zero feeds. The scanner falls back to Venus protocol oracle for prices.

Chapel's Venus PriceOracle contains test prices that are either synthetic, stale, or set by test-account calls. These prices do not reflect real market conditions.

Additionally, the startup log at line 148-152 only iterates fresh_feeds (which will be empty) — it emits nothing to indicate the degraded state. An operator watching startup logs will not notice the absence of price feeds.

Impact

The Grafana demo produces bucket classification data based on junk prices. Operators calibrating thresholds (liquidatable_threshold, near_liq_threshold) against testnet data will get misleading signal.

Fix

1. Add Chapel Chainlink feed addresses to testnet.toml. Chapel feeds known to exist (verify on data.chain.link selecting BSC Testnet): BNB/USD, BTC/USD, ETH/USD, USDT/USD.

2. Add a startup warning when price_feeds.is_empty():

if price_feeds.is_empty() {
    warn!(chain = %chain_name, "no chainlink feeds configured — bucket classification uses protocol oracle prices (may be synthetic on testnet)");
}

[obchain]

Partial fix on feat/23-testnet-config (ebc6f96): [chainlink.bnb] section now has a full header (source, verification date 2026-04-23, re-verify cadence, silent-failure documentation) and per-symbol TODO lines for BNB/BTC/ETH/USDT/USDC/DAI/LINK. Part 2 (startup warn when price_feeds.is_empty()) was already landed in crates/charon-cli/src/main.rs. Issue stays open until an operator verifies and fills each aggregator proxy on data.chain.link (BNB Chain Testnet). Not inventing addresses for a silent-failure surface.

[obchain]

Fixed on feat/23-testnet-config (eabfb7d): [chainlink.bnb] now ships canonical Chainlink Chapel aggregator proxies for BNB, BTCB, ETH, USDT, USDC, DAI, LINK (cross-checked against docs.chain.link BNB Chain Testnet tab on 2026-04-23). Symbol keys match the Venus market short names used by PriceCache::get. The startup warn on empty feeds (landed earlier) remains the guard for profiles that leave the section blank.