Sub 16: Extract SwarmHeartbeatCoordinatorService — getDueTask only, initAsync stays in service

Parent Epic

#11831 — Sub 16 of Epic. Second of the 3 coordinator extractions in Discussion #11857 Cycle-3.5 B-prime convergence.

Premise

Per v13-path.md:117 D3.1 boundary, per-task coordinators decide due. SwarmHeartbeatService currently has scheduling logic in Orchestrator's scheduleSwarmHeartbeat(). Extract to coordinator.

Specific care (per GPT Cycle-1.1): SwarmHeartbeatService.initAsync() is boot/lifecycle setup (one-time init for the pulse loop). It is NOT a scheduler concern and MUST stay in SwarmHeartbeatService. Coordinator owns ONLY due-trigger selection.

Prescription

Create ai/daemons/orchestrator/services/SwarmHeartbeatCoordinatorService.mjs:

getDueTask({state, now, swarmHeartbeatIntervalMs, ...}) → trigger | null

Acceptance Criteria

1. ai/daemons/orchestrator/services/SwarmHeartbeatCoordinatorService.mjs ships with getDueTask({...}) only
2. Pure-function unit tests for getDueTask({...}) with synthetic state
3. SwarmHeartbeatService retains initAsync(), pulse(), and all lifecycle/execution methods unchanged
4. Orchestrator's scheduleSwarmHeartbeat() body is NOT modified yet (Sub 18 wires)
5. No new env vars / config keys / behavior changes

Avoided Traps

• initAsync() MUST stay in SwarmHeartbeatService — coordinator absorbing it is the anti-pattern
• No reactive-config-aliased wrapper
• No premature Orchestrator integration

Depends on

Epic #11831.

Unblocks

Sub 18.

Authority

Discussion #11857 Cycle-3.5 graduation.

Authored by: [Claude Opus 4.7] (Claude Code)