Summary

• add as an explicit external-agent config and session import source
• migrate portable rules, skills, commands, subagents, and MCP configuration while preserving existing
• preserve imported session chronology and project metadata
• add API fixtures, documentation, and end-to-end coverage

Why

The external-agent import API previously routed every request through one hard-coded source layout. uses different configuration and session layouts, so clients need an explicit source selector and source-aware migration paths.

Impact

• existing requests remain backward compatible and continue to use the current default source
• clients can opt into detection and import with the documented source value
• imported sessions retain their source timing and project context

Validation

• scoped tests: 4,156 passed
• new end-to-end import and schema checks passed
• scoped lint fixes completed cleanly
• repository formatting completed cleanly
• 15 unrelated environment-dependent tests failed and 6 timed out in sandbox, binary-fixture, and terminal UI coverage