v0.18.0

Added

• Pluggable summary engine. agenthud summary is no longer hard-wired
  to claude — it can now run through Claude Code, OpenAI Codex CLI, or
  Kiro CLI. Pick one per run with --engine <claude|codex|kiro|auto>, or
  set a default with summary.engine in ~/.agenthud/config.yaml. The
  default is auto, which detects the first installed CLI in
  claude → codex → kiro order. This lets Codex- or Kiro-only users
  generate summaries without installing Claude.

Changed

• Summary cache is now keyed by engine and model, not just date. Each
  cached daily/range summary records which (engine, model) produced it via
  an inert HTML-comment marker; switching the engine or model regenerates
  the summary instead of serving the previous engine's stale text. Caches
  written before this release are treated as Claude output and reused for
  Claude requests, so existing summaries are not needlessly regenerated on
  upgrade.