v0.49.1 - Fix Duplicate Codex Skill Discovery

Bug fix

Fixes Codex discovering skill backups as duplicate installed skills.

• Skill backups now live under ~/.codex/init-agent-backups/skills/.
• init-agent sync automatically migrates legacy *.bak-* directories out of
  ~/.codex/skills/.
• Locally modified skills are still backed up safely before replacement.
• Added regression coverage ensuring only the active skill remains discoverable.

After upgrading:

pipx upgrade init-agent
init-agent sync