chore(release): bump to 0.11.0 and refresh changelog

Cuts the 0.11.0 release covering the RR simplification, RecursiveAgent
extraction into ace/core/, skillbook v2 schema, agentic SkillManager
rewrite, prompt caching defaults, and related observability/tooling
changes. Also drops the stale --cov-fail-under=25 reference from
CLAUDE.md to match the current pytest defaults.