refactor(codemode): namespace public types

[rekram1-node]

Summary

• audit the complete @opencode-ai/codemode root API and group related types under CodeMode.* and Tool.*
• make CodeMode.Input and CodeMode.Result both Effect schemas and their corresponding TypeScript types
• rename result types to CodeMode.Result, CodeMode.Success, and CodeMode.Failure while retaining descriptive names such as CodeMode.ExecuteOptions and CodeMode.ExecutionLimits
• keep the already-consistent OpenAPI.* namespace unchanged and update OpenCode, tests, and documentation

The runtime root is now limited to CodeMode, Tool, OpenAPI, ToolError, and toolError.

Testing

• bun test in packages/codemode (254 passed)
• bun typecheck in packages/codemode
• bun typecheck in packages/opencode
• focused OpenCode CodeMode tests (53 passed)
• Prettier check for changed files
• git diff --check