refactor: simplifying storage by giving it the client directly

[SimonRastikian]

Fixes #1645 by simplifying the triple generation part.

[claude]

PR title type suggestion: This PR restructures the storage API to take a client parameter. The type prefix should probably be refactor: to indicate code restructuring.

Suggested title: refactor: storage takes client

[claude]

Pull request overview

Simplifies TripleStorage::new to accept &Arc<MeshNetworkClient> directly instead of a separate my_participant_id + alive_participant_ids_query closure — matching the pre-existing PresignatureStorage::new shape. Adds a network::testing::new_test_client helper so unit tests can construct a MeshNetworkClient synchronously with all participants reported alive. Also drops a 4-line explanatory comment in robust_ecdsa::run_key_generation_client that appears unrelated to the storage-signature change.

Changes:

• TripleStorage::new signature: (clock, db, &client, threshold) — derives my_participant_id and the active-participants query from the client.
• EcdsaSignatureProvider::new and three cleanup tests updated to the new signature.
• New network::testing::new_test_client(participants, my_participant_id) returning a light-weight Arc<MeshNetworkClient> for unit tests (no live senders, no real connectivity).
• Removed the "reconstruction lower bound = t" comment in RobustEcdsaSignatureProvider::run_key_generation_client.

Reviewed changes

Per-file summary

File	Description
crates/node/src/providers/ecdsa/triple.rs	TripleStorage::new now takes &Arc<MeshNetworkClient>; the internal DistributedAssetStorage gets client.my_participant_id() and ecdsa_common::active_participants_query(client). Test helper new_triple_store updated.
crates/node/src/providers/ecdsa.rs	Call site simplified — the two closure arguments collapsed to &client.
crates/node/src/network.rs	Added pub fn new_test_client(...) in mod testing that wires up a TestMeshTransportSender with an empty senders map, a fresh NetworkTaskChannelManager, and an IndexerHeightTracker seeded from participants.
crates/node/src/assets/cleanup.rs	Three TripleStorage::new call sites in tests switched from Arc<Mutex<Vec<ParticipantId>>> closures to new_test_client.
crates/node/src/providers/robust_ecdsa.rs	Removes the 4-line "MaxMalicious = t − 1" comment from run_key_generation_client.

Findings

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

• crates/node/src/providers/robust_ecdsa.rs:127 — The removed comment on run_key_generation_client explained why robust-ECDSA can reuse cait-sith's internal keygen (reconstruction lower bound = MaxMalicious + 1 = t). This is exactly the kind of non-obvious "why" that project engineering standards say to keep. The sister function run_key_resharing_client still carries a similar remark at robust_ecdsa.rs:138, so the deletion also leaves the file inconsistent. This change is also unrelated to the stated PR goal ("simplifying the triple generation part") — consider restoring the comment or splitting this into its own PR with justification.
• crates/node/src/network.rs:924 — new_test_client builds the underlying TestMeshTransport with senders: HashMap::new(). Any test that reaches for send/new_channel_for_task on this client will fail with "Unknown recipient" at runtime. Worth calling out in the doc-comment (e.g. "no working transport — do not use for message sending; suitable only for read-only queries like all_alive_participant_ids") so future test authors don't reach for it in the wrong context.
• crates/node/src/network.rs:937-938 — IndexerHeightTracker::new(&participants) only seeds heights for the passed-in participants slice. If a caller passes a list that omits my_participant_id, set_height(my_participant_id, ...) would panic (heights.get(...).unwrap()), and all_alive_participant_ids would still push my_participant_id via its final result.push(...), silently masking the inconsistency. All current call sites include my_participant_id, so this is only a latent footgun — a debug_assert!(participants.contains(&my_participant_id)) inside new_test_client would make the contract explicit.

✅ Approved