Rollup node: DAL on Shadownet

What

This commit introduces a special case for the "Shadownet" test network. It hardcodes the DAL activation level to 1 when the rollup node is connected to this specific chain. This logic is applied within the DAL slot and page validation functions.

Why

Shadownet is a test environment where the DAL is misconfigured to activate at level 5,726,209. To ensure Shadownet remains a place where we can test deployment relaying on the DAL, this patch overrides the configured dal_activation_level when the Shadownet chain ID is detected.

Obviously, this only “works” because no real Tez are at stake on Shadownet.

How

A new constant, shadownet, is defined in dal_pages_request.ml using its B58-encoded chain ID.

The slot_id_is_valid function is modified to accept a chain_id parameter. Inside this function, it checks if the provided ID matches the shadownet constant. If it does, it locally overrides the dal_activation_level to be level 1.

The chain_id is now retrieved from the l1_ctxt in slot_pages and page_content using Layer1.get_chain_id. This ID is then passed down to page_id_is_valid and slot_id_is_valid, ensuring the correct validation logic is applied based on the connected L1 chain.

This patch is applied for both Seoul and Alpha.