feat(phase-3.1): agent entity types + metadata structs
EntityType enum extended with 3 agent types:
- AgentPrompt: track prompt templates, usage, quality
- AgentSkill: track learned capabilities, success rate, latency
- AgentDecision: track decisions, reasoning, outcomes
New module: agent_entity.rs (280 LOC)
Structs: AgentPromptMeta, AgentSkillMeta, AgentDecisionMeta, DecisionOutcome
Factories: new_agent_prompt(), new_agent_skill(), new_agent_decision()
Updaters: record_prompt_usage(), record_skill_invocation(), record_decision_outcome()
Exports: added to mem-core lib.rs
Tests: 8 new (prompt, skill, decision, outcome, usage stats,
invocation stats, round-trip, serialization)
Build: cargo build --release clean
Suite: 174 lib tests pass
rock
2f65f71bfb