feat(knowledge-bases): add waitForDatabase polling helper

[yashranaway]

Add waitForDatabase polling helper for knowledge bases

Summary

Adds a helper function to poll knowledge base database creation status until the database becomes ONLINE, eliminating the need for manual polling loops.

Changes

• New waitForDatabase helper function with error handling and configurable options
• Added method to KnowledgeBases class: client.knowledgeBases.waitForDatabase(kbId)
• Exported helper types and error classes
• Includes comprehensive error handling for timeout and failed states
• Added unit tests

Usage

// Before (manual polling)
while (true) {
   const kb = await client.knowledgeBases.retrieve('123e4567-e89b-12d3-a456-426614174000');
   if (kb.databaseStatus !== "ONLINE") continue;
}

// After (helper function)
const kb = await client.knowledgeBases.waitForDatabase('123e4567-e89b-12d3-a456-426614174000');

Fixes

Closes #5

[yashranaway]

@bbatha hey please let me know if you'd like anything changed/updates