Author runnable skill bodies via OpenAI-compatible codegen model

create_skill now writes a real predict/act body: the small decision model
still authors title + description (engine.generate), then a larger
OpenAI-compatible model (default qwen38-iq3s) writes the runnable code
against the SKILL.md contract. Bodies persist to data/skills/<cat>/<name>.py,
are hot-loaded via importlib, merged into the running tree, and the request
re-dispatches to the new leaf. The dashboard decision-flow view shows the
title/description with a writing badge while the body is being written.
Codegen failure degrades to a navigable stub.

.gitignore

@@ -4,6 +4,7 @@ __pycache__/
 data/decisions.jsonl
 data/runs.jsonl
 data/categories.json
+data/skills/
 data/drafts/
 .pytest_cache/
 config.json