Add MoonBit agent reflection APIs

[noise64]

• resolves GOL-46
• adds MoonBit runtime discovery, reflected JSON packing, caller-codec clients, and direct SchemaValue invocation
• resolves caller-codec identity metadata by environment-unique type name while keeping caller schemas authoritative
• uses asynchronous awaited invocation for live streams, validates required reflected outputs, and rejects streams in reflected trigger and scheduled calls
• shares decoded reflected schema definitions and adds stream-graph regression coverage
• renames the language guide to golem-agent-reflection-moonbit and regenerates skill-derived docs

Verification

• MoonBit reflection check and build
• MoonBit reflection tests: 6 passed
• full MoonBit SDK host-import tests: 260 passed
• MoonBit reflection scenario harness dry-run
• documentation drift check
• stacked on Scala SDK: add agent reflection and dynamic invocation #3812

[github-actions]

📖 Docs preview: https://docs-oc8wazx4a-golem-cloud.vercel.app

Built from commit 1dadeafabdf83d16e8bf1665617715d8e7a6d5a7 by docs.yaml.