Add long-tail automation rules from LLM-assisted decompilation research

[bgyss]

Summary

• land notes from Chris Lewis’s "Long Tail of LLM-Assisted Decompilation" blog and document the extracted findings in docs/llm-assisted-decompilation-long-tail.md.
• update plans, roadmap, research, and automation/security specs with long-tail mitigation requirements (similarity ranking, task lanes, guardrails, metrics, retry budgets, policy hooks).
• revise SPEC-210, SPEC-250, and SPEC-260 to capture deterministic candidate ordering, long-tail metadata, and protected edits for unattended loops.

Testing

• Not run (not requested)