docs: v6.6.0 catch-up — verified subset - #59

Docs-only PR (10 files, +55/−4) adding v6.6.0 behavior notes to the EVM parity, precompile, and node pages. Two blocking issues: the effectiveGasPrice example in evm/transactions.mdx now contradicts the EIP-1559 formula this same PR documents, and the new Autobahn newHeads section asserts live behavior for a consensus protocol the rest of the docs explicitly label "upcoming / in development" — claims that also fall outside the PR's own verification evidence table.