[hackathon] feat: add HostNotifier trait and decouple node from ExExContext

[prestwich]

Summary

• Add new signet-node-types crate with HostNotifier trait, HostNotification, and HostNotificationKind types — no reth dependencies
• Refactor signet-node to be generic over HostNotifier instead of depending on ExExContext<Host> directly
• Remove reth ExEx dependency from signet-node-config (RPC config moved to host-reth in follow-up PR)
• SignetNodeBuilder now accepts any HostNotifier implementation

PR 2 of 5 in the host context adapter refactor.
Precursor: #104

Test plan

• cargo clippy -p signet-node-types --all-features --all-targets
• cargo clippy -p signet-node --all-features --all-targets
• cargo clippy -p signet-node-config --all-features --all-targets
• cargo clippy -p signet-node-config --no-default-features --all-targets
• cargo +nightly fmt

🤖 Generated with Claude Code

[prestwich]

[Claude Code]

Note: CI failures here are expected — test fixes land in #108 (fix/node-tests-host-notifier). PRs #104, #105, #106, #107, and #108 are intended to be merged as a unit; they are broken out into separate PRs for review isolation.

[prestwich]

[Claude Code]

Code review

Found 3 issues:

1. node-tests uses the removed .with_ctx() API, which will cause a compile failure. The PR removes .with_ctx(ExExContext) from SignetNodeBuilder and replaces it with .with_notifier(), but crates/node-tests/src/context.rs and crates/node-tests/tests/db.rs still call .with_ctx(ctx).

node-components/crates/node-tests/src/context.rs

Lines 151 to 153 in 382521c

	let (node, mut node_status) = SignetNodeBuilder::new(cfg.clone())
	.with_ctx(ctx)
	.with_storage(Arc::clone(&storage))

node-components/crates/node-tests/tests/db.rs

Lines 33 to 35 in 382521c

	let (_, _) = SignetNodeBuilder::new(cfg.clone())
	.with_ctx(ctx)
	.with_storage(Arc::clone(&storage))

2. crates/node/src/alias.rs is orphaned. The PR removes mod alias from lib.rs and removes the reth dependency from Cargo.toml, but leaves alias.rs on disk. The file imports from reth which is no longer a dependency, so it would fail to compile if ever re-included.

node-components/crates/node/src/alias.rs

Lines 1 to 10 in 382521c

	use alloy::{consensus::constants::KECCAK_EMPTY, primitives::Address};
	use core::{
	fmt,
	future::{self, Future},
	};
	use eyre::OptionExt;
	use reth::providers::{StateProviderBox, StateProviderFactory};
	use signet_block_processor::{AliasOracle, AliasOracleFactory};
	/// An [`AliasOracle`] backed by a reth [`StateProviderBox`].

3. if/else instead of functional combinator in start_inner (CLAUDE.md says "ALWAYS prefer functional combinators over imperative control flow")

node-components/crates/node/src/node.rs

Lines 186 to 192 in 382521c

	// Set the head position and backfill thresholds on the notifier
	let host_height = if last_rollup_block == 0 {
	self.constants.host_deploy_height()
	} else {
	self.constants.pair_ru(last_rollup_block).host
	};
	self.notifier.set_head(host_height);

🤖 Generated with Claude Code

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