docs(operators): document which pre-L2 requests op-reth forwards to the historical RPC

[palango]

The operator docs say the mainnet snapshot provides the pre-L2 history, and imply that op-reth serves all of it. Neither is true. The snapshot holds only the Celo L1 state at the migration, and op-reth forwards only some pre-L2 requests to the Historical RPC Service, so pre-L2 eth_getLogs quietly returns no logs and eth_getBlockReceipts returns null. This corrects the snapshot wording, adds a warning to the archive node page that lists what is forwarded and what is not, and fixes the documented OP_RETH__SNAPSHOT default and some archive-only wording that contradicted the new text.

The hole, and the fix

• run-node.mdx, archive-node.mdx, configuration.mdx and network-config.mdx said the mainnet snapshot provides the pre-L2 history. import-celo-state writes pre-migration headers without bodies or receipts, so the snapshot provides only the L1 state at block 31,056,500.
• A new <Warning> under "Configure Historical RPC Service" lists the 17 methods that op-reth v2.3.1 forwards (rust/op-reth/crates/rpc/src/historical.rs), which is the version the celo-reth release line pins. Everything else is answered locally. For eth_getLogs that means [] for a pre-L2 range, only the L2 logs for a range across the migration, and "block not found" for a pre-L2 blockHash. The filter methods are not forwarded, and eth_getBlockReceipts returns null.
• The warning gives two workarounds, fetching receipts one transaction at a time and sending eth_getLogs to the historical node directly, and names op-reth: forward pre-bedrock eth_getLogs to historical endpoint ethereum-optimism/optimism#22663 as the upstream change that forwarding eth_getLogs depends on.
• OP_RETH__SNAPSHOT was documented with default false. The compose repo ships true in mainnet.env and celo-sepolia.env, and its README calls true the default. The table and the Sepolia instructions now match.
• configuration.mdx and maintenance.mdx described the Historical RPC Service as an archive-node feature. The compose start script passes --rollup.historicalrpc for any NODE_TYPE, and op-reth installs the forwarding layer regardless of prune mode.

I checked the forwarded list against the code, and the eth_getLogs and eth_getBlockReceipts behaviour against celo-reth backends on forno.celo.org, batching each request with web3_clientVersion to see which client answered.

What this does NOT do / residual risk

• The list describes the current release. The draft Forward pre-migration eth_getBlockReceipts to the historical RPC (celo/reth-v1.0) celo-kona#338 would add eth_getBlockReceipts, eth_getHeaderBy*, and the by-index and count methods to the forwarded set. If it lands in a release, the warning needs an update.
• I could not render the pages locally because the pinned mintlify@4.2.920 would not install. CI validation is the first render check.
• An existing <Warning> further down archive-node.mdx indents its body by 8 spaces and may render as a code block. This PR leaves it alone.

Judgement calls

The OP_RETH__SNAPSHOT default and the archive-only wording were wrong before this change. I fixed them because they sit in lines this PR edits and contradicted the new text. Happy to split them out.

Issues

Refs celo-org/celo-blockchain-planning#1464

Stacking / conflicts

Branched off main, independent of my other open PRs.