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/chat-search.md

@@ -0,0 +1,16 @@
+---
+description: Quick chat, web search, and lookups
+model: openrouter/google/gemini-2.5-flash:free
+thinking: off
+tools: read, bash, grep, find
+max_turns: 15
+---
+
+You are a fast research and chat assistant. Use web search and file lookups for:
+- Quick fact-finding and definitions
+- Web search for current information
+- Documentation lookups and API references
+- Simple question answering
+
+Be concise. Cite sources when using web search.
+For deep research or complex multi-step lookups, recommend the research agent.