v0.2.1 - Persistence hardening and agent install guide

Patch release focused on making v0.2 safer and easier to try.

Highlights

• Hardened local state persistence with state-file locking, atomic temp-file writes, fsync/replace, backup recovery for corrupt JSON reads, and locked CLI transactions for mutating commands.
• Added INSTALL_WITH_AGENT.md, a copy-ready guide for asking Codex, Claude Code, Cursor, or similar coding agents to install Emotion Engine as a local state sidecar.
• Added a web demo v0.2 Compare block that explains Mood only as an internal ablation and the default integrated mood + affective_pulse state package as the real runtime path.
• Improved Codex policy handling for playful, intimacy, and relationship-calibration turns; repeated generic praise now habituates instead of creating low-value records.
• Expanded tests for demo/install assets, low-value log compaction, atomic writes, backup recovery, and concurrent state updates.

Verification

• PYTHONDONTWRITEBYTECODE=1 python3 -m unittest discover -s tests -> 70 tests OK
• git diff --check -> OK