Per-run data now lives in ~/.arc/runs/ while daily CLI log files
stay in ~/.arc/logs/. Renames: logs_root → run_dir (RunConfig field,
Handler trait param, all handlers), logs_dir → run_dir (CLI arg,
local variables), default_logs_base → default_runs_base (path fn).
Adds DB migration 002 to rename workflow_runs.logs_dir → run_dir.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>