refactor(aidd-dev): lean the assert skill for small models #1077

Problem

aidd-dev:03-assert is 5 files and 979 words: three actions (assert, assert-architecture, assert-frontend) that iterate the project's coding assertions until they pass. Under opencode with Mistral small and medium models, every extra file read re-sends the whole context, and the iterate-until-green loop forces a re-read on each turn.

Scope

• Same method as the brainstorm and plan skills: mermaid router with action paths, recipe steps with the loop explicit, one Output per action, rules only where the action owns them, no duplicate between actions and references.
• Check the router on opencode with mistral-small-2603 and mistral-medium-2604.

Acceptance criteria

• The pre-commit gates pass, with fewer words than today.
• On the same scenarios, Claude haiku and sonnet and mistral-medium-2604 reach green assertions at least as often as the original, at lower or equal cost.
• The loop stops when the assertions pass or when a failure needs the user.

Prior art in this repo

• The brainstorm skill issue refactor(aidd-refine): lean the brainstorm skill for small models #1071 and the plan skill issue.
• aidd_docs/memory/coding-assertions.md.

Out of scope

• plan, implement, review: separate issues.
• Changing the project's own assertions.