Fix model ToolSupport declarations for capable models

[Kamilbenkirane]

Priority: High
Related: #199

Several tool-capable models have incorrect ToolSupport declarations, silently disabling functionality.

Models to audit:

• OpenAI: gpt-4-turbo, gpt-4 missing ToolSupport despite being capable
• xAI: grok-2-vision-1212 has no ToolSupport constraint at all
• Mistral: All models declare ToolSupport(tools=[]) — Mistral Large supports function calling
• DeepSeek: ToolSupport(tools=[]) blocks user-defined tools despite mapper supporting them
• Groq: Most models have empty tools despite Llama/Qwen supporting function calling
• HuggingFace: Same issue as DeepSeek

Files:

• src/celeste/modalities/text/providers/openai/models.py
• src/celeste/modalities/text/providers/xai/models.py
• src/celeste/modalities/text/providers/mistral/models.py
• src/celeste/modalities/text/providers/deepseek/models.py
• src/celeste/modalities/text/providers/groq/models.py
• src/celeste/modalities/text/providers/huggingface/models.py

[Kamilbenkirane]

Investigation findings:

• The bulk of this issue (Mistral/DeepSeek/Groq/HuggingFace "blocking tools") is invalid. ToolSupport(tools=[]) only validates Tool instances — dict tools bypass the constraint entirely. User-defined function tools work fine on all these providers today.
• The real gap: 4 legacy models are missing TextParameter.TOOLS entirely in their parameter_constraints, so they don't advertise tool support in metadata:
  • gpt-4-turbo, gpt-4, gpt-3.5-turbo (OpenAI) — all support tools per OpenAI docs
  • grok-2-vision-1212 (xAI) — likely supports tools but delisted from xAI docs
• Fix: add TextParameter.TOOLS: ToolSupport(tools=[]) to these 4 models.