Add MCP exposure, resource binding, and claims schemas

[rg4444]

Summary

• add declarative MCP exposure metadata to the package manifest schema and provide a manifest schema alias
• introduce schemas for resource bindings, policies claims declarations, and workspace MCP exposure flags
• document MCP schema conformance boundaries and add alignment notes appendix for future work

Testing

• ajv validate -s schemas/manifest.schema.json -d examples/**/*.json (fails: ajv CLI unavailable in environment)
• ajv validate -s schemas/resource-binding.schema.json -d examples/**/*.json (fails: ajv CLI unavailable in environment)

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[chatgpt-codex-connector]

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