Add stream callbacks

[svilupp]

• Added a new EXPERIMENTAL streamcallback kwarg for aigenerate with the OpenAI and Anthropic prompt schema to enable custom streaming implementations. Simplest usage is simply with streamcallback=stdout, which will print each text chunk into the console. The system is modular enabling custom callbacks and allowing you to inspect received chunks. See ?StreamCallback for more information.

Example usage:

using PromptingTools
const PT = PromptingTools

# Simplest usage, just provide where to steam the text
msg = aigenerate("Count from 1 to 100."; streamcallback = stdout)

streamcallback = PT.StreamCallback()
msg = aigenerate("Count from 1 to 100."; streamcallback)
# this allows you to inspect each chunk with `streamcallback.chunks`

# Get verbose output with details of each chunk
streamcallback = PT.StreamCallback(; verbose=true, throw_on_error=true)
msg = aigenerate("Count from 1 to 10."; streamcallback, model = "claudeh")

[codecov]

Codecov Report

Attention: Patch coverage is 83.33333% with 39 lines in your changes missing coverage. Please review.

Project coverage is 91.83%. Comparing base (d04c737) to head (593ce9c).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/streaming.jl	88.07%	26 Missing ⚠️
src/llm_openai.jl	0.00%	8 Missing ⚠️
src/llm_anthropic.jl	37.50%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #203      +/-   ##
==========================================
- Coverage   92.27%   91.83%   -0.45%     
==========================================
  Files          45       46       +1     
  Lines        4129     4359     +230     
==========================================
+ Hits         3810     4003     +193     
- Misses        319      356      +37     

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