feat: wire available foreign chains API into node and e2e tests

[anodar]

Node side changes from: #3484

Work towards: #3475

Followup on: #3511

[claude]

PR title type suggestion: This PR adds new functionality for foreign chain transaction verification and configuration, so it should use the feat: prefix.

Suggested title: feat: add foreign chain transaction verification support

[claude]

Pull request overview

Adds the node-side wiring for the new register_foreign_chains_config / get_foreign_chains_configs contract API introduced in #3484, sent alongside the legacy register_foreign_chain_config so a single node binary works on both pre- and post-upgrade contracts. The fake indexer gains an equivalent registration path plus a threshold-based recompute, and a new e2e test asserts the per-node configs surface on the contract after auto-registration.

Changes:

• coordinator.rs: send both legacy and new registration transactions on startup.
• indexer/types.rs: new ChainRegisterForeignChainsConfigArgs variant; method/gas wiring.
• indexer/tx_sender.rs: accept the new variant in observe_tx_result.
• indexer/fake.rs: handle the new tx; recompute an "available" set with threshold semantics; refactor the legacy registration to share the cross-participant intersection helper.
• e2e-tests: new cluster view helper and e2e test available_foreign_chain_by_node__should_reflect_auto_registered_configs.

Reviewed changes

Per-file summary

File	Description
crates/node/src/coordinator.rs	Send both RegisterForeignChainConfig and RegisterForeignChainsConfig on startup.
crates/node/src/indexer/types.rs	Add new args type and enum variant; map to REGISTER_FOREIGN_CHAINS_CONFIG method and MAX_GAS.
crates/node/src/indexer/tx_sender.rs	Treat new variant as TransactionStatus::Unknown (fire-and-forget).
crates/node/src/indexer/fake.rs	Add available_foreign_chains_by_node + available_foreign_chains fields; implement register_foreign_chains_config with threshold-based recompute; refactor legacy path through record_node_chains.
crates/e2e-tests/src/cluster.rs	Add view_available_foreign_chain_by_node calling GET_FOREIGN_CHAINS_CONFIGS.
crates/e2e-tests/tests/foreign_chain_configuration.rs	New e2e test asserting auto-registered per-node configs.
crates/e2e-tests/tests/common.rs	Add AVAILABLE_FOREIGN_CHAINS_BY_NODE_PORT_SEED = 22.

Findings

Non-blocking (nits, follow-ups, suggestions):

• crates/node/src/indexer/fake.rs:58 — available_foreign_chains (and by extension the threshold recompute at fake.rs:154-170) is dead code: the field is written but never read, and there is no getter exposing it. Either expose it via a method that a unit test uses to lock in the threshold semantics, or drop the field and the recompute. As written it is untested logic that will silently drift from the real contract (e.g. if the real contract's whitelist intersection rule changes, this stays out of sync with no test surfacing the divergence).
• crates/node/src/indexer/types.rs:194 — TODO references #3485, while the matching TODOs in coordinator.rs:402 and tx_sender.rs:302 reference #3475. Worth aligning so a future cleanup grep finds all three sites.
• crates/e2e-tests/src/cluster.rs:842 — method name view_available_foreign_chain_by_node is slightly misleading: it calls GET_FOREIGN_CHAINS_CONFIGS, which returns the per-node registered configs, not the available (threshold-passed) set. Consider view_foreign_chains_configs_by_node to match the contract method's intent and avoid future confusion with GET_AVAILABLE_FOREIGN_CHAINS.
• crates/e2e-tests/tests/foreign_chain_configuration.rs:158-181 — the test asserts cardinalities only (2 covering Solana, 1 empty) and does not check which nodes are which. Keying the assertion on the per-node TLS public key (which the cluster exposes) would catch a regression where, e.g., node 2's empty registration overwrites the wrong TLS-key slot.

Approved