[codex] Fix Paper and CarbonChat chat forwarding

[TypeThe0ry]

What changed

• Forward Paper chat reliably, including Paper async chat events and CarbonChat fallback behavior.
• Add Velocity CarbonChat compatibility so CarbonChat early chat events are forwarded into AstrBotAdapter.
• Default Minecraft -> AstrBot message forwarding to all chat by using an empty messageForward.prefix.
• Update README and the deployment prompt to document GitHub Actions artifacts, /sid/NapCat session targets, and the all-chat forwarding default.

Why

CarbonChat on Velocity bypassed the normal chat listener path, and the old * forwarding prefix meant normal player chat was not bridged to AstrBot/QQ.

Validation

• GitHub CI success on latest head: https://github.com/EllanServer/AstrBotAdapter/actions/runs/28712220921
• Local integration test with Velocity + CarbonChat using GitHub-built jars: normal chat codex_github_all_20260704161206 produced 消息已转发 in Velocity logs.