Oracles: add a Pyth Pro entry, fix the Chainlink Data Streams note, link the consumer demos

Start with skills/standards/ecosystem.md and inspect its Oracles section and the linked Pyth Pro and Chainlink field notes and comparison. Update the entries with the requested Pyth Pro details, corrected Data Streams note, examples, and oracle selection guidance. Done when the section covers all requested facts and links, with the staleness and source selection rules included.

The Oracles section of skills/standards/ecosystem.md lists Reflector, DIA and Chainlink. Three gaps, checked on 12 November 2026:

1. No Pyth Pro entry. Pyth Pro (formerly Lazer) is live on Stellar since 8 September 2026. Verifier contracts: mainnet CACZ3GBAKUPIAFRILUFO27J5RUH5GJ2VSJ46LP6GJYSKGDRTQ5MS3HCH, testnet CAYFT5JE3UQTKT4Q6ZOZK4FXVYVT6RE3MFC7STA4UB6WAEGBT65MRU52. Pull model: fetch a signed update from the Pyth Pro REST API, verify it on chain with verify_update(Bytes), crate pyth-lazer-stellar-sdk 0.4.0 (pins soroban-sdk ^26.1). The verifier is stateless, so freshness is the consumer's job. A free Terminal key is a 14-day trial of a sample set; XLM/USD needs the Starter plan. Guide: https://docs.pyth.network/price-feeds/pro/integrate-as-consumer/stellar

2. Chainlink entry: the Data Streams line is out of date. "Needs an allowlisted account" is wrong. The Stellar verifier has no access controller; anyone can call verify(signed_report, sender). What gates Streams is the API subscription: no free tier since 1 September 2026. Verifier contracts: mainnet CAKA3NBYPC6OBEUEGNIYGNYG3ES2GPQK736B5SR7ASGUXRDAKXI2JCQI, testnet CA7GVHWH4GRHE6GI7MHEKQZAOYO4GE7KRGSU3EOS3HYJRVLX3XEA4ONQ. Two more facts for the Data Feeds lines: a frozen feed reaches callers as Error(Contract, #109), and get_min_decimals is 18 for XAUM Reference Rate and USPC NAV.

3. No worked consumer examples. Two public repos read these oracles from a Soroban contract on testnet, with unit tests, scripts and a read-only page:

   • Pyth Pro: https://github.com/kaankacar/stellar-pyth-pro-demo (field note: docs/field-note/pyth-pro-field-note.md)
   • Chainlink Data Feeds: https://github.com/kaankacar/stellar-chainlink-demo (field note: docs/field-note/chainlink-field-note.md)
   • Pyth Pro, Chainlink Data Feeds and Reflector side by side, with the staleness rule each one needs: https://github.com/kaankacar/stellar-chainlink-demo/blob/main/docs/field-note/oracle-comparison.md

Proposed change: a #### Pyth Pro entry, the Data Streams fix in the Chainlink entry, and an Examples line under the Reflector, Chainlink and Pyth Pro entries that points at the repos and the comparison. I can open the PR.

4. No guidance on which oracle to pick. An agent that reads this skill cannot tell when to use Reflector, Chainlink Data Feeds or Pyth Pro. The comparison above has the facts; the skill needs the rule. Proposed text for the Oracles section:

   • Reflector (public Pulse oracles): free, SEP-40, 14 decimals, a new price every 5 minutes. Pick it for a Stellar-native asset, for DEX prices, or when SEP-40 compatibility matters. Staleness rule: reject when now - timestamp > 2 x resolution.
   • Chainlink Data Feeds: free, one proxy per network, 18 decimals, a new price on a 0.5 percent move or every 24 hours. Pick it for a shared reference rate on BTC, ETH, XLM, LINK, USDT, USDC, EURC, gold or the NAV feed, and when the protocol already uses Chainlink elsewhere. Staleness rule: reject when now - timestamp > heartbeat, and expect a quiet-day price to be hours old.
   • Pyth Pro: paid API, pull model, sub-second prices with bid and ask, the consumer brings the signed update and the verifier checks only the signatures. Pick it for perps, liquidations and anything that needs the price at execution time. Staleness rule: reject on feedUpdateTimestamp and skip carried-forward feeds.
   • Chainlink Data Streams: the same pull model as Pyth Pro, paid subscription, no free tier. Same staleness rule, on expiresAt and observationsTimestamp.
   • Two sources for funds: anything that liquidates or mints against a price should read two oracles and refuse on divergence. On 12 November Chainlink and Reflector mainnet XLM/USD differed by 6 basis points and 14 minutes at the same moment.