feat(solana-indexer): add types module scaffolding

[tilacog]

Description

Adds the type definitions for the types/ module listed in the crate-layout spec.

This is PR 2 in the sequence; later PRs (traits (PR 3), then component structs (PR 4)) consume these types.

Changes

• Added crates/solana-indexer/src/types/ with one file per module from the spec:

  • wire.rs: wire-format types, for the Yellowstone gRPC protobuf types
  • channel.rs: payload types for messages exchanged between the Ingester and Decoder component
  • events.rs: domain event taxonomy
  • commitment.rs: types for tracking Solana commitment levels
  • dead_letter.rs: dead-letter primitives
  • recovery.rs: recovery state
  • errors.rs: error types for this crate
  • tx.rs: transaction context
  • metrics.rs: observability counters

• Declared pub mod types; in lib.rs so the module compiles.

How to test

1. cargo check -p solana-indexer
2. cargo +nightly fmt --all -- --check
3. cargo clippy --locked --workspace --all-features --all-targets -- -D warnings

No unit tests are included: the modules contain only type definitions, with no logic to exercise until the traits in PR 3 are introduced.

[gemini-code-assist]

Code Review

This pull request introduces the solana-indexer crate, which defines domain types for a Solana settlement indexer, including channel messages, commitment tracking, dead-letter handling, errors, events, metrics, recovery flows, and transaction helpers. A high-severity issue was identified in channel.rs where the PartialEvent struct is missing the half: PartialHalf field described in its documentation, which is required for the watchdog to reconstruct events. Adding this field also means PartialEvent must derive Clone instead of Copy due to heap-allocated types in PartialHalf.

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[gemini-code-assist]

The doc comment for PartialEvent states that "each delivery carries the half that just landed," but the struct definition is missing the half: PartialHalf field. Without this field, the watchdog cannot receive or hold the actual data halves to match and reconstruct the full event. Additionally, since PartialHalf contains heap-allocated Box types, PartialEvent cannot derive Copy and should only derive Debug, Clone.

Suggested change

	#[derive(Debug, Clone, Copy)]
	pub struct PartialEvent {
	/// Slot the partial was observed at.
	pub slot: u64,
	/// Transaction signature the partial corresponds to.
	pub signature: Signature,
	}
	#[derive(Debug, Clone)]
	pub struct PartialEvent {
	/// Slot the partial was observed at.
	pub slot: u64,
	/// Transaction signature the partial corresponds to.
	pub signature: Signature,
	/// The half that just landed.
	pub half: PartialHalf,
	}