Support separation of streaming from PromptingTools.jl

[Sixzero]

This PR enables StreamCallbacks.jl to work independently after streaming functionality was moved out of PromptingTools.jl core.

Related PR

Works with: svilupp/PromptingTools.jl#307

Changes Made

Integration with PromptingTools.jl:

• Added PromptingTools dependency to Project.toml
• Import AbstractStreamCallback from PromptingTools
• Implement configure_callback! and streamed_request! methods for PromptingTools integration

Interface Updates:

• Use PromptingTools' AbstractStreamCallback as base type
• Create AbstractHTTPStreamCallback subtype indicating HTTP backend in the package
• Remove duplicate Base methods (now handled by PromptingTools)

Moved streaming precompilation from PromptingTools to here

Benefits

• Clean Architecture: Proper separation of concerns between packages
• Backward Compatibility: Existing streaming code continues to work unchanged

Usage

After both PRs merge, streaming works exactly as before:

using PromptingTools, StreamCallbacks
msg = aigenerate("Hello"; streamcallback=StreamCallback())

Version bumped to 0.7.0 to reflect the architectural change.