🚧 Rewrite continous simulation.

README.md

@@ -185,6 +185,56 @@ Configuration options: `--no-web`, `--web-port <n>` or env
 benches (all mutating endpoints answer 403). Plain HTTP — keep the
 port inside the bench network.
 
+## Plant environments (continuous simulation)
+
+A **plant environment** simulates the physical world around the
+distributed I/O: per deterministic tick it reads what the PLC
+commanded (DO/AO), runs your plant physics, and writes what the field
+now shows (DI/AI) — the sensors the PLC reads back. Environments run
+**until manually stopped** (Ctrl+C / `docker stop`), optionally ending
+sooner via an `is_done()` criterion.
+
+Attach one to a live Modbus server (wall-clock-paced 10 ms ticks):
+
+```bash
+wago-sim serve --node config/pump_node.yaml --port 5020 \
+               --env envs.pump_station_env:PumpStationEnv
+```
+
+or run headless (unpaced, for plant-model development):
+
+```bash
+wago-sim sim --node config/pump_node.yaml \
+             --env envs.pump_station_env:PumpStationEnv
+```
+
+**Authoring one** is a small subclass — override `model()`:
+
+```python
+# myenvs/tank.py
+from wago_sim.scenario.plantenv import PlantEnv
+
+class TankEnv(PlantEnv):
+    def model(self, state, dt_s):
+        pump_on = bool(state.by_code("DO0.0"))   # PLC command
+        level   = float(state.by_code("AI0.0"))  # current field
+        return {"AI0.0": level + (-5.0 if pump_on else 1.0) * dt_s}
+
+Env = TankEnv        # `--env myenvs.tank` picks this up
+```
+
+API surface (spec FR-8.2.14–17): `observe()` returns every
+DI/DO/AI/AO channel (I/O codes, names, values) plus aliases and
+degradation parameters; `apply()` writes DI/AI (the field);
+`force()` writes DO/AO master-side (headless runs, fault setup);
+`is_done()` optional end; `reset()` deterministic replay. Reference
+forms: `pkg.mod:ClassName`, `pkg.mod:factory`, or `pkg.mod` with
+`Env`/`make_env`. The shipped example is
+`envs/pump_station_env.py` (tank + pump physics with a low-level
+switch). Scenario-continuous mode (§8 YAML: datasets, degradation,
+invariants) remains available for scripted soak runs on the same
+engine ticks.
+
 ## Documentation
 
 - `docs/spec/software-spec.md` — the software specification
@@ -404,17 +454,18 @@ reporting, snapshots, and the gym-style `PlantEnv`. 30 new tests
 Datasets are **optional**: signal logic runs in parallel with CSV
 streaming, or entirely without it.
 
-- [x] Plant environment `scenario/plantenv.py` (FR-8.2.14–16, requested
-      2026-10-04): gym-style `PlantEnv` — deterministic engine-owned
-      tick clock (never wall-clock); per tick:
-      `observe()` returns the WAGO input image in engineering units
-      (channel values, names, per-type I/O codes, ranges, sim-time);
-      the decision source decides; `apply()` writes the decided
-      outputs through the datastore's internal paths (mirrors/
-      statistics/watchdog stay consistent). Existing `plugins:`
-      become thin adapters; external (non-Python) decision sources
-      step the env over a socket; one decision source per output
-      alias per tick (ownership conflicts are errors).
+- [x] Plant environment `scenario/plantenv.py` (FR-8.2.14–17, reworked
+      2026-10-04 to environment-first): standalone `PlantEnv` —
+      `observe()` returns ALL modules (DI/DO/AI/AO channels, per-type
+      codes, names, parameters); `apply()` writes the FIELD side
+      (DI/AI) by default; `force()` writes DO/AO master-side (mirrors/
+      statistics/watchdog stay consistent); `model()`/`is_done()`
+      override hooks (subclass authoring, FR-8.2.17); `reset()`
+      deterministic. Runners: `serve --env ...` wall-clock-paced
+      alongside Modbus, runs until stopped; `sim --env ...` headless
+      unpaced until is_done()/Ctrl+C. Example: `envs/pump_station_env.py`.
+      Verified live: PLC coil write → env physics → level registers
+      drain/refill over Modbus.
 - [x] `scenario/datasets.py` — streaming CSV playback for designated
       inputs (OPTIONAL driver): header-driven time column,
       `interpolation: linear|hold`, `repeat` with seamless seams,