ic-engine v2.4.1 — adapter/engine split + bare-import sweep.

Unblocks InvestorClaw v2.3.0. Adds INVESTORCLAW_SKILL_DIR env override so adapters can point engine at their own user-data root while engine-code paths stay at the package install location.

50 files swept for bare imports (from config.X -> from ic_engine.config.X etc).

Codex review clean.