fix: point the oracle tutorial at Pragma's Miden v0.15 oracle

[Keinberger]

Overview

The Pragma oracle tutorial (oracle_data_query + oracle_reader.masm + oracle_tutorial.md) couldn't run: it pointed at Pragma's old pre-v0.15 oracle, which the v0.15 client rejects. Pragma has since redeployed on Miden 0.15 (astraly-labs/pragma-miden, miden-client 0.15.3), so this points the tutorial at the new deployment and gets it reading a live price again.

Key Changes

• masm/accounts/oracle_reader.masm: update the two stale hardcoded values used by the execute_foreign_procedure call: the get_median procedure MAST root and the oracle account id. The BTC/USD faucet pair (1:0) is unchanged.
• rust-client/src/bin/oracle_data_query.rs: default the oracle address to Pragma's current testnet oracle (mtst1apadf2szkxqkcyt7x2znuggv9qkhccam) so cargo run works with no args; a bech32 id passed as the first argument still overrides it.
• docs/src/rust-client/oracle_tutorial.md: update the masm block, the run command, and the expected-output transcript to match, plus a note that Pragma's addresses change between testnet iterations.

Rationale

I took the new get_median MAST root and the oracle id felts from Pragma's own get_median_procedure_hash() rather than hardcoding a guess, then ran it against the live oracle: it returns is_tracked = 1 and a real BTC/USD median. A wrong root would fail the foreign procedure call, not return a price.

The publisher id word in the oracle's storage is laid out as [prefix, suffix, 0, 0] with this client version, so the tutorial keeps reading [w[0], w[1]]. Pragma's own examples/consume-price reads [w[3], w[2]] and currently panics (UnknownAccountIdVersion(0)) against the released miden-client, so I did not follow it there.

Tests

Ran oracle_data_query against testnet: is_tracked=1, median 6439689500000, exit 0. cargo test --doc (17 passed, 0 failed) and prettier --check are green, and the doc's no_run program is byte-identical to the binary.

Open Questions

1. Decimals: get_median returns only the raw fixed-point median; the decimals live per-entry in Pragma's feed. The raw value only makes sense for BTC at 8 decimals (about $64,396.89), so that is what the doc says, but the old feed used 6. Happy to adjust if you know the exact precision.
2. Fragility: Pragma's addresses change between testnet iterations, so these hardcoded values will need re-updating on each redeploy. Worth tracking if we want the tutorial to stay green on its own.

[Keinberger]

@brianseong could you give this one a review when you get a chance? 🙏

[BrianSeong99]

Approved 👍