refactor(core): type safety and performance improvements

[jdmanring]

Summary

Core package type safety and performance:

• L-14,L-15: Use satisfies for NO_TOOLS, add type guard for rateLimit payload
• L-16: Make ConfigSource.detail required, update all constructors
• M-03: Resolve shellReadOnlyChecker deprecation ambiguity
• L-18,L-19: Use array push in-place for flatMapTextParts and splitCommands

Files Changed

• packages/core/src/utils/*.ts
• packages/core/src/config/config.ts

Type of Change

• Refactor
• Performance improvement
• Bug fix
• New feature

Testing

• Unit tests pass
• Integration tests pass