fix(plugin): enable EverMind by default and complete host manifests

[ypflll]

Summary

Enable EverMind SkillHub by default across all supported SkillCorpus plugin integrations and fix missing or inconsistent host manifests.

• Enables EverMind by default for WorkBuddy, OpenClaw, Hermes, Raven, and the TypeScript engine.
• Keeps ClawHub and skillhub.cn enabled by default.
• Allows users to disable any remote source by setting its endpoint to an empty string.
• Adds the root .codebuddy-plugin/marketplace.json required for WorkBuddy to discover the SkillCorpus marketplace.
• Updates the OpenClaw manifest so its remote-source defaults match the runtime configuration.
• Adds regression and release checks for manifest paths, plugin names, versions, and default endpoint consistency.
• Updates installation documentation to disclose that remote sources are enabled by default.

Verification

• TypeScript engine: 45 tests passed
• Python engine: 103 tests passed
• WorkBuddy: 32 tests passed; typecheck, build, and package verification passed
• OpenClaw: 29 tests passed; typecheck, build, and package verification passed
• Hermes: 22 tests passed
• Raven: 8 tests passed; 3 host-dependent tests skipped
• Marketplace and OpenClaw manifest JSON validation passed
• Release version and manifest consistency checks passed