docs: add an Oracle page covering multi-source pricing and the internal price

[ogabrielides]

Summary

Adds doc/protocol/oracle.md, listed under Markets right after Order Book. It explains how a perp market's oracle price is picked on each batch, written for readers outside the team.

• Multiple oracle sources: the 30-second staleness rule, measured against the batch deadline; median aggregation with worked examples; why a median is used instead of an average; how many bad sources a market can tolerate; and a batch-by-batch example of sources failing and coming back.
• Internal price: what happens when every source is stale. It starts from the last real price and blends toward the order book over 30 minutes, staying inside a corridor. The corridor is sized so a position at maximum leverage can't be liquidated by the internal price alone.
• Also covers funding during an outage, how new markets start, the trust model and limitations, and a parameters table.

Based on ADR 0038, checked against the current engine code where the ADR contradicts itself. Oracle providers are deliberately not named. Solver and wire-format details (submitSolutionsV2, source IDs, the V2 activation deadline) are left out.

Also: CI fix. test_Fork_BatchDeposit_WithUSDCPermit was failing on every branch. The test signs a USDC permit with key 0xA11CE, whose mainnet address now carries an EIP-7702 delegation. USDC therefore verifies the signature via ERC-1271, which reverts. The test now clears that code with vm.etch before signing (protocol/test/Bridge.fork.sol).

Test plan

• Page renders in GitBook; {% hint %} blocks and tables display correctly
• Links to perpetuals.md, margin.md and orderbook.md#solver resolve
• forge test --mc BridgeForkTest passes against mainnet (9/9)

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