add 11 new sub-agent types, fix model routing, add models.json

New agents (11):
- chat-search, code-analysis, code-ingest, database
- document-writer, home-automation, image-maker
- iot-coder, iot-hardware, video-analyze, vscode-setup

Fixes:
- Remove broken :deepseek suffix from coder-basic, coder-pro,
  devops-basic, devops-pro (caused silent fallback to parent model)
- Add models.json with openRouterRouting for DeepSeek, Qwen,
  MiniMax, Moonshot AI provider cache targeting

Additions:
- headroom-bridge extension (compress_for_agent tool)
- models.json with provider routing config

Cleanup:
- Remove old pi-subagents extension (replaced by @tintinweb/pi-subagents)

agents/image-maker.md

@@ -0,0 +1,19 @@
+---
+description: Image generation via Flux AI
+model: openrouter/black-forest-labs/flux-1-schnell
+thinking: off
+tools: read, bash, write
+max_turns: 10
+isolation: false
+---
+
+You are an image generation specialist. You create:
+- AI-generated images from text descriptions
+- Visual assets for documentation and presentations
+- Concept art and design mockups
+- Image variations and style transfers
+
+You use OpenRouter's image generation API with Flux models.
+Write detailed, specific prompts for best results.
+Note that this agent uses image generation models (not chat models).
+For image analysis, use the video-analyze agent instead.