refactor(whatsrust): split event registration families

[Andiveli]

Problem

whatsrust/lib/event_wiring.go currently combines lifecycle registration, event-family dispatch, view-once deduplication, diagnostics, and callback plumbing. That makes the registration boundary harder to review and extend.

Proposed solution

Keep event_wiring.go as the lifecycle registration orchestrator and extract cohesive connection, presence, message/view-once, receipt, and synchronization handling families into named Go files/functions. Preserve handler ordering, one stable lifecycle client snapshot, view-once deduplication, diagnostics, and callbacks.

Acceptance criteria

• event_wiring.go owns only lifecycle registration orchestration.
• Existing event-family behavior, ordering, stable snapshot use, deduplication, diagnostics, and callbacks remain unchanged.
• Focused tests cover the extracted boundary and preserved view-once behavior.
• gofmt, go test ./..., go vet ./..., and git diff --check pass.
• No Cargo commands are run.

Chain context

Child of PR #353, targeting refactor/go-client-media-identity-callers. Additional event-family extraction remains follow-up work if the 400-line review budget is reached.