Replace concrete module type switch with ExecutionTrackerSetter interface in cmd/server/main.go #62

Problem

cmd/server/main.go around lines 280–295 has a switch on concrete module types:

case *module.QueryHandler:
    qh.SetExecutionTracker(app.executionTracker)
case *module.CommandHandler:
    ch.SetExecutionTracker(app.executionTracker)

This pattern requires modifying the server every time a new module type needs an execution tracker.

Fix Direction

Define an ExecutionTrackerSetter interface:

type ExecutionTrackerSetter interface {
    SetExecutionTracker(ExecutionTrackerProvider)
}

Have eligible modules implement it. The engine ranges over services calling the interface method — no more switch.

Note

Depends on the serverApp god object refactor and the type assertions refactor being merged first.

Context

See docs/DEFERRED_ISSUES.md — Architecture section.