Load persistent memory for configured agents

[shouc]

Summary

• load persistent agent memory into the agent system prompt when an agent resource declares memory: user|project|local
• add a dedicated runtime helper module for agent-memory path resolution and prompt assembly
• add focused tests for project/local agent memory loading and prompt integration

Audit scope

This was a fresh parity pass on latest master in a repo-local worktree after checking open PR scope first.

Explicitly excluded overlapping in-flight work:

• Import Claude Desktop MCP servers into Puffer #24 audit/claude-parity-gaps-5 owns Claude Desktop MCP import parity
• Document ignore-memory policy in the runtime prompt #23 audit/claude-parity-gaps-4 owns ignore-memory policy prompt guidance
• Load workspace and user memory into the runtime prompt #22 audit/claude-parity-gaps-3 owns runtime loading of workspace/user memory files
• Restore Claude-compatible /compact local command flow #21 audit/claude-parity-gaps-2 owns the /compact local-command parity fix
• Restore full Claude-compatible tool prompts for OpenAI #20 audit/claude-parity-gaps owns the OpenAI tool-prompt parity fixes

The concrete non-overlapping gap here was subagent memory:

• Puffer's agent resource model already exposes memory: user|project|local
• but the runtime ignored it when building agent system prompts
• Claude's reference agent runtime loads persistent agent memory for agents that opt into it

Testing

• cargo test -p puffer-core agent_memory -- --nocapture
• cargo test -p puffer-core agent_runtime -- --nocapture

Notes

• The implementation uses Claude-compatible .claude/agent-memory and .claude/agent-memory-local paths, plus the same PUFFER_HOME-derived .claude home root that Puffer already uses for team artifacts.
• For parity verification in the repo-local worktree, I temporarily mounted the existing local references/ corpus into the worktree so the audit could compare against the Claude reference tree. No references/ content is included in this branch.