Add Amp harness support

[yourconscience]

Amp can read ~/.agents/skills/ through standard conventions but is not currently managed by dotagents.

Scope:

• Detect Amp installation and config paths
• Skills: verify native skill loading from ~/.agents or mirror into Amp's skill root
• MCP servers: render into Amp's native MCP config format
• Hooks: investigate Amp's hook/lifecycle surface
• Roles/agents: investigate if Amp has a native agent/role format

Amp is listed in the README compatibility note but has no adapter. This would promote it to a managed harness.