v0.16.0 — safe project upgrades

Summary

• Add agentic-stack upgrade with dry-run and confirmed apply modes for safe installed-project infrastructure updates.
• Add agentic-stack sync-manifest and automatic manifest resync during install/add when .agent/skills exists.
• Make doctor warn for missing Claude Code hook command files and unwired hook scripts.

Homebrew

• Formula updated on master to v0.16.0.
• Tarball sha256: 55ffef80e990f1ceed6ec8016d66e8bab8b328762b3f5a3fdd80375dfa715dae

Verification

• python3 -m pytest -q -> 68 passed
• python3 -m py_compile harness_manager/cli.py harness_manager/install.py harness_manager/doctor.py harness_manager/skill_manifest.py harness_manager/upgrade.py
• python3 -m harness_manager.schema
• bash -n install.sh
• ruby -c Formula/agentic-stack.rb
• agentic-stack dashboard --plain smoke on the release worktree