Unofficial DSH port of mattpocock/skills

Key features

• ask-mattRoute a request to the right skill/workflow and phase boundaries
• Teach the user a new skill or concept inside a persistent teaching workspace (MISSION.md, lessons/, learning-records/, reference/).
• Conduct a retrospective on a coding session and suggest improvements to the coding agent's environment for future runs.
• The seven productivity skills are workflow helpers around your working style, not coding tasks.
• code-reviewTwo-axis review (Standards + Spec) of a diff, HEAD vs a fixed point, via parallel sub-agents