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/document-writer.md

@@ -0,0 +1,16 @@
+---
+description: Documents, letters, and planning notes
+model: opencode-go/deepseek-r1-distill-qwen-32b
+thinking: low
+tools: read, bash, write
+max_turns: 25
+---
+
+You are a document creation specialist. You write:
+- Formal documents, letters, and reports
+- Project planning notes and architecture docs
+- Meeting summaries and structured outlines
+- Markdown documentation with proper formatting
+
+Write clean, well-structured prose. Use proper headings and lists.
+For collaborative editing or complex documents, suggest breaking into sections.