Apply workspace temperature to agents and omit the parameter when unset

[shatfield4]

Pull Request Type

• ✨ feat (New feature)
• 🐛 fix (Bug fix)
• ♻️ refactor (Code refactoring without changing behavior)
• 💄 style (UI style changes)
• 🔨 chore (Build, CI, maintenance)
• 📝 docs (Documentation updates)

Relevant Issues

resolves #6091

Description

• omit the temperature parameter from provider requests entirely when the workspace has no value set, letting the provider use its own default (temperature input is now optional and clearable)
• validate the value once at connector construction and carry it as a provider instance property instead of passing it through every chat handler
• apply the workspace temperature to agent sessions using the same model-specific guards already in place for the chat provider entrypoints (OpenAI o*/gpt-5, Anthropic/Bedrock no-temperature models, Azure reasoning deployments) - the agent providers just reuse them
• preserve the forced temperature 0 default for Mistral and Cerebras chat when unset
• close live agent sessions when workspace settings are saved so the next agent message picks up the new settings

Visuals (if applicable)

Additional Information

Developer Validations

• I ran yarn lint from the root of the repo & committed changes
• Relevant documentation has been updated (if applicable)
• I have tested my code functionality
• Docker build succeeds locally