lokahi: Rust multi-chain interop node (tracking)

Tracking issue for **lokahi** (Hawaiian *lōkahi*: unity/agreement) — the Rust multi-chain interop node built from kona-node components at `rust/lokahi/`, mirroring op-supernode's protocol behavior (timestamp-lockstep cross-safety, deposits-only replacement, superroot/syncStatus) with a different architecture: per chain, a **ChainController** (kona's EngineActor, extended) as hub with derivation/gossip/sequencer spokes; cross-chain, one **interop actor** whose cross-safe promotions are the only way the FCU safe label moves. op-supernode is not replaced — lokahi is additive and wire-compatible with existing supernode RPC consumers.

Design docs (Notion, under 🌴 Lokahi): [Architecture Brainstorm](https://app.notion.com/p/3c1f153ee16281cfaa08dde809fb6c0d) · [Implementation Plan](https://app.notion.com/p/3c1f153ee162815ebf8ef132c161b518)

Phases (sub-issues; each phase carries its work items as sub-issues — dependencies are named per item so parallel work is visible):
- Phase 0: #22519 — delete op-supervisor-era interop legacy from kona (in progress)
- Phase 1: #22520 — kona shared-component refactors
- Phase 2: #22521 — lokahi N-chain scaffolding (no interop)
- Phase 3: #22522 — interop actor, cross-safe happy path
- Phase 4: #22523 — invalidation
- Phase 5: #22524 — RPC parity, sequencing, test harness

Broadly parallelizable from the start: #22529 (metrics label), #22531 (multi-chain L1 watcher), #22534 (kona-interop rules), #22535 (interop stores), #22539 (op-reth reorg spike).

🤖 *Co-created with Claude (Fable 5)*

Start with the Architecture Brainstorm and Implementation Plan under 🌴 Lokahi, then inspect rust/lokahi/ and the phase sub-issues beginning with #22519. This tracking issue is complete only when its scoped phases and work items are completed; choose a specific sub-issue before looking for an implementation entry point or tests.

Written by the indexing model from the issue text.