Added a sampler-ready simulation architecture with a stable responder plugin contract (`SessionInfo`, `Observation`, `Action`, `Feedback`, lifecycle hooks).
Added a centralized responder adapter and policy layer (`strict|warn|coerce`) used by `StimUnit.capture_response()` and `StimUnit.wait_and_continue()` so injected responses flow through one validation seam.
Added deterministic simulation plumbing (seed/session/rng), structured JSONL simulation audit logs, and replay helpers.
Added plugin loader/config support (built-ins + external import-path responders) and a demo external responder.
Moved runtime context/session plumbing under `psyflow.sim.context` so responder/runtime logic stays in `sim`.
Updated template MID task and T000006 MID task to standardize trial context fields (`trial_id`, `phase`, `deadline_s`, `valid_keys`, `condition_id`, `task_factors`) for simulation readiness.
Added contract and determinism tests for responder plugins and sim runs.
CLI redesign: moved to one root command `psyflow` with subcommands `init`, `qa`, `sim` for compact, terminal-friendly usage.