Remove AtLeastOne/AtMostOne type constraints for simpler type inference

[konard]

Summary

This PR simplifies the type machinery by removing AtLeastOne and AtMostOne utility types, as requested in #8. The key changes are:

• Removed AtLeastOne/AtMostOne utility types from types.ts - these complex conditional types were hurting TypeScript's ability to infer types correctly
• Made previously constrained fields optional at the type level (e.g., validationResults, problems, allowedValues, suggestedValues)
• Preserved the conditional type for value/inline object branching in ToolCallSuccess - this was explicitly requested to stay
• Runtime validation via Zod schemas in @tool2agent/schemas still enforces the AtLeastOne/AtMostOne constraints at runtime

Before vs After

Before:

// Complex utility types that hurt inference
export type AtLeastOne<T, K extends keyof T = keyof T> = Omit<T, K> &
  { [P in K]: Required<Pick<T, P>> & Partial<Omit<T, P>>; }[K];

export type AtMostOne<T, K extends keyof T = keyof T> = Omit<T, K> &
  ( | { [P in K]?: never }
    | { [P in K]: Required<Pick<T, P>> & Partial<Record<Exclude<K, P>, never>> }[K] );

// Used in types like:
export type RecordFailureFeedback<T> = AtLeastOne<{
  validationResults: AtLeastOne<{...}>;
  problems: NonEmptyArray<string>;
}>;

After:

// Simple optional fields - constraints enforced at runtime
export type RecordFailureFeedback<T> = {
  validationResults?: {...};
  problems?: NonEmptyArray<string>;
};

Files Changed

• packages/types/src/types.ts - Removed AtLeastOne/AtMostOne exports
• packages/types/src/tool2agent.ts - Simplified types using optional fields
• packages/schemas/src/schema-tools.ts - Removed type imports (runtime validation unchanged)
• packages/types/test-d/*.ts - Updated type tests for new behavior
• packages/schemas/test/schemas.test.ts - Updated test expectations

Test plan

• Build passes (pnpm build)
• Lint passes (pnpm lint)
• Format check passes (pnpm format:check)
• Type tests pass (packages/types/test:types)
• Schema tests pass (packages/schemas/test)
• AI package tests pass (unit and types)

Note: Two pre-existing runtime test failures exist in the AI package (missing API key and a JSON.stringify edge case) - these are unrelated to this PR.

Fixes #8

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[konard]

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