v0.6.1 — Lean agent reads and safe retention

Highlights

• graph and search now keep observations and skill bodies lazy.
• Added preview-first purge for stale terminal sessions and tasks.
• Added Bash, Elvish, Fish, PowerShell, and Zsh completion generation.
• Durable knowledge and skills are protected from purge.

Verification

• make check passes.
• Coverage: 62.60% (1,053/1,682 lines).
• Release binaries are built by the tag workflow for Linux x86_64 and macOS ARM64.