feat: integrate publish preconf fn to permissionless node

[PoulavBhowmick03]

Summary

• Addedget_secret_key() to Signer for commitment signing
• Built L2BlockV2Payload from slot info and anchor block
• Called post_preconf_requests from preconfirmation_drivet in main_block_preconfirmation_step fn
• Added a preconfirmation_driver function to Operator as it is one of the fields in Node, to use while calling the PreconfirmationDriver

[Copilot]

Pull request overview

This PR integrates preconfirmation publishing functionality into the permissionless node by enabling it to construct L2 block payloads and submit preconfirmation commitments to the preconfirmation driver.

Changes:

• Added get_secret_key() method to Signer for extracting secp256k1 private keys needed for commitment signing
• Implemented L2BlockV2Payload construction in main_block_preconfirmation_step using slot info and anchor block data
• Integrated post_preconf_requests call to publish both transaction lists and signed commitments to the preconfirmation driver

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
common/src/signer/mod.rs	Added get_secret_key() method to extract secp256k1::SecretKey from PrivateKey signer variant
common/Cargo.toml	Added secp256k1 dependency required for commitment signing
Cargo.lock	Updated with secp256k1 dependency
permissionless/src/node/config.rs	Added coinbase and l1_height_lag fields to NodeConfig for L2 payload construction
permissionless/src/lib.rs	Initialized new NodeConfig fields with preconfer address and l1_height_lag
permissionless/src/node/operator/mod.rs	Added getter method preconfirmation_driver() to access the driver for posting requests
permissionless/src/node/mod.rs	Implemented preconfirmation publishing logic in main_block_preconfirmation_step
permissionless/src/l2/preconfirmation_driver.rs	Changed rpc_client visibility to public and removed dead_code annotation from post_preconf_requests

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