feat: Added support for GitHub Copilot SDK as LLM Provider

[Harshalj2108]

Description

This PR introduces the GitHub Copilot SDK as a supported LLM Provider, allowing developers with active Copilot CLI subscriptions to leverage industry-leading models seamlessly.

Closes #343

Changes Made

• Dependency Addition: Added github-copilot-sdk to requirements.txt.
• CopilotProvider Implementation: Created a new provider in models.py bridging the Copilot Python SDK.
• Sync-Async Bridge: Implemented a ThreadPoolExecutor in CopilotProvider to gracefully wrap the Copilot SDK's native asynchronous event loop inside hiring-agent's synchronous provider interface. This prevents any event loop collision issues.
• Error Bubbling: Explicitly intercepts and raises SessionErrorData to ensure SDK issues (like unauthenticated states) properly bubble up to the pipeline rather than failing silently.
• Model Support Updates: Updated prompt.py to map the most recent Copilot-supported models.

Prompts Configuration (Before / After)

Before:

# Model provider mapping
MODEL_PROVIDER_MAPPING = {
    # Google Gemini models
    "gemini-1.5-pro": ModelProvider.GEMINI,
    "gemini-1.5-flash": ModelProvider.GEMINI,
    # ...
}
**After**
# Model provider mapping
MODEL_PROVIDER_MAPPING = {
    # Google Gemini models
    "gemini-1.5-pro": ModelProvider.GEMINI,
    # ...
    
    # GitHub Copilot models
    "gpt-5.5": ModelProvider.COPILOT,
    "gpt-5.6-luna": ModelProvider.COPILOT,
    "gpt-5.6-sol": ModelProvider.COPILOT,
    "gpt-5.6-terra": ModelProvider.COPILOT,
    "claude-sonnet-5": ModelProvider.COPILOT,
    "claude-opus-4.8": ModelProvider.COPILOT,
    "claude-fable-5": ModelProvider.COPILOT,
    "mai-code-1-flash": ModelProvider.COPILOT,
}

[Copilot]

Pull request overview

This PR adds GitHub Copilot SDK as an additional LLM provider so the app can route supported model names to Copilot (alongside existing Ollama and Gemini providers).

Changes:

• Added github-copilot-sdk dependency.
• Introduced ModelProvider.COPILOT and a new CopilotProvider implementation in models.py.
• Extended model parameter defaults and model→provider mapping to include Copilot model names, and wired provider initialization in llm_utils.py.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 6 comments.

File	Description
requirements.txt	Adds github-copilot-sdk to dependencies.
prompt.py	Adds Copilot model names to MODEL_PARAMETERS and MODEL_PROVIDER_MAPPING.
models.py	Adds ModelProvider.COPILOT and implements CopilotProvider.chat() using the Copilot SDK.
llm_utils.py	Instantiates CopilotProvider when the selected model maps to ModelProvider.COPILOT.

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[sp2hari]

Thanks for this — the no-API-key angle (running on an existing Claude Code / SDK login) is a neat idea. We're standardizing on the config-driven provider layer from #298: Claude API access now lands via a providers.json block using Anthropic's OpenAI-compatible endpoint (#365), and we're not taking on subprocess/SDK-based providers at this time (extra dependencies + a separate code path outside the config model). Closing on that basis — not a reflection of the work, which was solid. Appreciate it.