[Go SDK] examples/triggers-demo-go end-to-end demo + skill docs

[santoshkumarradha]

Summary

Land a Go counterpart to examples/triggers-demo/ and add a Go-flavored section to the skill reference so the agentfield-multi-reasoner-builder skill emits correct Go scaffolds.

Part of the epic #508. Depends on the public surface and dispatch path from the sibling issues.

Scope

New Files

File	Purpose
examples/triggers-demo-go/main.go	Three deterministic reasoners — handle_payment (Stripe), handle_pr (GitHub), handle_tick (cron). Same shape and memory-write semantics as examples/triggers-demo/agent.py
examples/triggers-demo-go/Dockerfile	Build the Go agent into a container
examples/triggers-demo-go/docker-compose.yml	Control plane + Go agent + shared demo secrets — drop-in replacement for the Python demo
examples/triggers-demo-go/README.md	Quick-start + UI tour
examples/triggers-demo-go/scripts/fire-events.sh	Symlink or copy of examples/triggers-demo/scripts/fire-events.sh — same script, same signed payloads

Modified Files

File	Change
skills/agentfield-multi-reasoner-builder/references/triggers.md	Add a Go-flavored section showing the same trigger declarations in Go so the skill produces correct Go scaffolds

Acceptance

• cd examples/triggers-demo-go && docker compose up brings up control-plane + go-agent
• ./scripts/fire-events.sh (the existing script, unmodified) fires Stripe + GitHub events that dispatch successfully
• Cron trigger fires every minute and produces memory writes equivalent to the Python demo
• Trigger sheet at localhost:8080/ui/triggers shows three triggers, all enabled, with signature: valid on dispatched events
• Run-detail Inbound section populates for runs originating from the Go agent

References

• Parent epic: [Epic] [Go SDK] Trigger system parity (#506) #508
• Python demo: examples/triggers-demo/
• Skill reference: skills/agentfield-multi-reasoner-builder/references/triggers.md
• Trigger system: Feat universal plugin based triggers #506