feat(scenarios): add the Pyth Core Compatible receiver price feed template

crates/core/src/scenarios/README.md

@@ -13,7 +13,7 @@ For Surfpool to understand how to serialize and deserialize account data, it nee
 Protocols that are natively supported by Surfpool will have their IDLs included by default.
 
 **Currently supported protocols:**
-- **Pyth v2** - Price oracle with 4 price feed templates (SOL/USD, BTC/USD, ETH/BTC, ETH/USD)
+- **Pyth v2** - Price oracle with a price feed template for the Pyth Core receiver (`pyth-price-feed-v2`) and one for the Pyth Core Compatible receiver (`pyth-core-compatible-price-feed-v2`); both keep the price they write published
 - **Jupiter v6** - DEX aggregator with TokenLedger manipulation template
 - **Switchboard On-Demand** - On-demand oracle with QuoteAccount override template
 - **Kamino** – Lending (v1.23.0), Scope oracle, Farms, Swap/LIMO, Earn vaults and Liquidity, across six programs. See [protocols/kamino/README.md](./protocols/kamino/README.md)

crates/core/src/scenarios/protocols/pyth/core-compatible/v2/README.md

@@ -0,0 +1,36 @@
+# Pyth Core Compatible
+
+Pyth runs two price receivers on Solana, both deployments of the `pyth_solana_receiver` program, as
+listed on [Pyth's Solana contract addresses](https://docs.pyth.network/price-feeds/contract-addresses/solana):
+
+| Receiver | Program | Template |
+|---|---|---|
+| Pyth Core | `rec5EKMGg6MxZYaMdyBfgwp4d5rB9T1VQH5pJv5LtFJ` | `pyth-price-feed-v2` |
+| Pyth Core Compatible | `rec2HHDDnjLfj4kE7VyEtFA1HPGQLK33259532cRyHp` | `pyth-core-compatible-price-feed-v2` |
+
+They hold separate price accounts for the same feeds, and a consumer reads the accounts of one of
+them. Take the price account from the consumer's own account that names it.
+
+# Keep-alive
+
+Nobody publishes Pyth prices on a surfnet, so both templates import a
+[keep-alive](../../../../README.md#keep-alive): from the slot an override of a template plays until
+the network is reset, Surfpool writes the Clock's unix seconds to `price_message.publish_time` and
+the slot to `posted_slot` every slot, time travels included. It does so for every price account of
+that template's receiver the surfnet has loaded, including feeds no override names and, from the
+next slot, feeds a transaction loads later, so a liquidation that reads the borrower's other feeds
+finds them fresh. The price, confidence and EMA fields keep their values. To keep one feed stale on
+purpose, override it with `keepAlive: false`; it then ages against the Surfnet clock.
+
+# IDL
+
+`idl.json` is the IDL the program publishes in its Anchor IDL account
+`raeUSn8gguFWVFs4iw3YathYM3mdb95W5Bfiu3tqE7F` (`pyth_solana_receiver` 0.2.1, legacy format, sha256
+`9ec4718f66a71fc524ecdd533770ca5a8a3984f8e1fb603f01f5e31ff0ab0caa`), converted with
+`anchor idl convert --program-id rec2HHDDnjLfj4kE7VyEtFA1HPGQLK33259532cRyHp` (anchor-cli 0.31.1,
+output sha256 `29ab79ef705a3429b3ced2b1222e1b5efdcd4b40fed547177d31c16ebd8473fc`).
+
+One change is made before the conversion: the account names `priceUpdateV2` and `twapUpdate` are
+written `PriceUpdateV2` and `TwapUpdate`, as the program's Rust types are named. Anchor derives an
+account's discriminator from its name, and only the capitalized names give the discriminator the
+live price accounts carry.