feat: refactor agent abstraction layer for Amp SDK compatibility

[rubenmarcus]

Summary

Refactor the agent abstraction layer to support Amp SDK as a first-class agent backend.

Linear: ENG-1462

Changes

1. Add amp to AgentType union in src/loop/agents.ts
2. Add Amp agent config to AGENTS object (detection command, run command, args mapping)
3. Generalize the agent interface to support Amp's tool-use patterns
4. Ensure the abstraction can handle Amp's 3 modes: smart, rush, deep
5. Add Amp to the agent detection loop (detectAgent())

Current Architecture

// src/loop/agents.ts
type AgentType = 'claude-code' | 'cursor' | 'codex' | 'opencode' | 'unknown';

Needs to become:

type AgentType = 'claude-code' | 'cursor' | 'codex' | 'opencode' | 'amp' | 'unknown';

Files

• src/loop/agents.ts (main changes)
• src/types.ts (if AgentType is exported)

Depends On

• Issue K (Research Amp SDK API surface)