Enhance TypeScript strictness with explicit types and runtime validation

[Copilot]

Replaced loose typing (Record<string, unknown>) with explicit types and added runtime validation for LLM API responses. Enabled additional strict compiler options.

Type System Improvements

• LLM Service types: Created PartialGameData and GeneratedGameData types derived from Game interface
• Environment variables: Replaced as unknown as assertions with proper WindowWithEnv and ImportMetaEnv interfaces
• GameCreate component: Uses typed PartialGameData instead of generic records

Runtime Validation

Added isValidGameData() type guard validating API response structure:

function isValidGameData(data: unknown): data is GeneratedGameData {
  if (!data || typeof data !== 'object') return false;
  const obj = data as Record<string, unknown>;
  
  return typeof obj.title === 'string' &&
    typeof obj.description === 'string' &&
    Array.isArray(obj.framework) &&
    typeof obj.minParticipants === 'number' &&
    // ... validates all required fields
}

Responses are validated before type casting, preventing runtime type mismatches.

Compiler Options

Added to both tsconfig.app.json and tsconfig.node.json:

• noUncheckedIndexedAccess - prevents unsafe array/object access
• noImplicitOverride - requires explicit override keywords
• noPropertyAccessFromIndexSignature - enforces bracket notation for index signatures

Zero any types remain in codebase.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Enhance TypeScript Strictness and Typing</issue_title>
<issue_description>Review the TypeScript codebase and replace any 'any' types or loosely-typed sections with stricter, explicit types. Enable 'strict' mode in tsconfig.json for improved type safety and reliability across the project.
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Enhance TypeScript Strictness and Typing #14

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