feat: streaming support for query responses

[0xneobyte]

Problem

The query method waits for the complete response before returning anything to the caller. For long-form answers this introduces noticeable latency — the caller receives nothing until generation is fully complete. Every major AI SDK (Anthropic, OpenAI, Gemini) exposes streaming as a first-class feature.

Proposed Behaviour

Add a queryStream method that yields response chunks as they arrive rather than waiting for the full response.

for await (const chunk of client.queryStream({ query: 'What is Python?' })) {
  process.stdout.write(chunk)
}

• Existing query() is unchanged
• queryStream() returns an async iterable
• Citations and metadata returned at end of stream

Files to Modify

File	Change
src/client.ts	Add queryStream method returning an async iterable
src/types.ts	Add streaming chunk type
src/index.ts	Export new types

Acceptance Criteria

• queryStream() yields text chunks progressively as they arrive
• Existing query() behaviour is unchanged
• Citations accessible at end of stream
• Stream can be cancelled mid-way without errors
• Full TypeScript types on all new methods and interfaces