fix(agent) scope steering

[afjcjsbx]

📝 Description

This PR introduces Scoped Steering, moving away from a single global steering queue to a session-isolated architecture. It ensures that messages arriving during an active agent turn are only injected if they belong to the same session scope, preventing cross-conversation message leakage. Additionally, this update adds support for multimodal steering (media/images) and improves the agent loop reliability by adding new polling points to catch late-arriving messages.

🗣️ Type of Change

• 🐞 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 📖 Documentation update
• ⚡ Code refactoring (no functional changes, no api changes)

🤖 AI Code Generation

• 🤖 Fully AI-generated (100% AI, 0% Human)
• 🛠️ Mostly AI-generated (AI draft, Human verified/modified)
• 👨‍💻 Mostly Human-written (Human lead, AI assisted or none)

🔗 Related Issue

Fixes #

📚 Technical Context (Skip for Docs)

• Reference URL: N/A
• Reasoning: - Isolation: Previously, any message arriving while an agent was busy could be "steered" into the active turn, regardless of the sender or chat. Now, messages are matched against the activeScope.
• Requeueing: Messages not belonging to the current scope are now put back onto the inbound bus to be processed normally later.
• Multimodal: Enabled Media refs in steering messages, ensuring images are resolved via the media pipeline before being sent to the LLM.
• Loop Integrity: Added a check after direct LLM responses. If a user sent a message while the LLM was "thinking," the agent now continues the turn instead of delivering a stale response.

🧪 Test Environment

• Hardware: PC / Server
• OS: Linux (Debian/Ubuntu)
• Model/Provider: OpenAI GPT-4o / DeepSeek-V3 (Tested with multimodal capabilities)
• Channels: Telegram, Discord

📸 Evidence (Optional)

Click to view Logs/Screenshots

• Verified TestAgentLoop_Steering_DirectResponseContinuesWithQueuedMessage passes.
• Verified TestAgentLoop_Continue_PreservesSteeringMedia for multimodal support.
• Confirmed non-scoped messages are requeued correctly via TestDrainBusToSteering_RequeuesDifferentScopeMessage.

☑️ Checklist

• My code/docs follow the style of this project.
• I have performed a self-review of my own changes.
• I have updated the documentation accordingly.

[yinwm]

LGTM!

Review Summary:

• ✅ Scoped steering isolation - clean design for preventing cross-conversation leakage
• ✅ Backwards compatible with fallback queue (__manual__ scope)
• ✅ Comprehensive test coverage (scope isolation, direct response polling, multimodal support)
• ✅ Documentation updated alongside code changes
• ✅ Concurrency-safe (proper mutex usage in steeringQueue)

No blocking issues found. Ready to merge.