Render Nexus service-call events in workflow history timelines

[rmcdaniel]

Confirmed defect

The worker HTTP regression in durable-workflow/server#140 now reaches real Nexus dispatch, but history projection throws UnhandledMatchError from HistoryTimeline::summaryFor for ServiceCallStarted. The match does not cover any of the four ServiceCall event variants. This prevents a valid service-operation workflow task from completing and also breaks timeline inspection of those events.

Acceptance

• Explicitly render all four defined ServiceCall history event types without hiding unknown event kinds behind a generic default.
• Test persisted event projection for started, completed, failed, and cancelled calls, including sparse optional metadata.
• Keep request payloads and caller secrets out of human-readable summaries.
• Run the focused regression and normal repository checks, publish a patch, and verify the Server HTTP dispatch regression against that package.

This is a direct dependency of server#138, not additional speculative scope.

[rmcdaniel]

Fixed by #488 and published as Workflow 2.0.6 at af1b743. All four service-call variants have explicit projection coverage, including sparse metadata and persisted model reload. Full implementation database/coverage/Laravel checks passed (run 34191440855), and published-package plus Laravel upgrade verification passed (run 34192337301). Server #140 now uses the released Packagist dependency, and the actual worker HTTP dispatch/completion regression passes against it without a source overlay. Server image publication remains tracked by server#138.