Release 0.3.0

First part of Milestone 1: Forecast Error sensors scoring the thermal
model against reality, forecast trajectories, Learning Progress and Last
Sample sensors, rejected-sample and poll-outcome counters, plus lint
and rollback-contract tests. README explains forecast accuracy, the
30-minute learning wait after a restart and where Developer Tools now
lives. ROADMAP marks the items now backed by tests; AUDIT records the
evaluation design and evidence. Still observation-only.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -1,4 +1,4 @@
-# Heating MPC 0.2.3 — custom integration for Home Assistant OS
+# Heating MPC 0.3.0 — custom integration for Home Assistant OS
 
 **Experimental, observation-only (shadow mode).** It **never** changes the Generic Thermostat, the physical relay, the boiler's setpoint, `heat/off`, or Comfort/Away/Sleep. No Docker add-on, MQTT or InfluxDB connection is needed.
 
@@ -55,6 +55,12 @@ Entities (entity IDs may vary):
   ON/OFF plan). These assume the MPC's plan is executed; while Generic Thermostat
   controls the relay they are **counterfactual**.
 - `binary_sensor.heating_mpc_proposed_heat` — **hypothetical** heating demand (unavailable until ready).
+- **Heating MPC Learning Progress** — how close the least trained room is to being
+  used for forecasts (100 % = ready); attributes show the sample counts and what is
+  required.
+- **Heating MPC Last Sample** — what the last poll did for learning (for example
+  *Learned*, *Relay switched*, *Waiting for radiators to settle*); its history shows
+  when learning happens.
 - **Heating MPC Forecast Error 15/30/60/120 min** — how far the thermal model's
   forecasts were from what actually happened (see *Forecast accuracy*).
 
@@ -71,6 +77,21 @@ Entities (entity IDs may vary):
 
 ## Diagnostics
 
+Start with **Learning Progress** and **Last Sample**. For details, open the
+**Heating MPC Status** entity's attributes. In recent Home Assistant versions
+Developer Tools is at the bottom of **Settings** (or press Cmd/Ctrl+K and type
+"developer"); its **States** tab lists every attribute.
+
+**Why learning starts about 30 minutes after a restart.** The model learns how
+much the radiators warm each room, so it needs to know how warm the radiators are.
+It estimates this from when the relay last switched (20-minute time constant).
+After a Home Assistant restart that time is unknown, so learning waits until the
+estimate is within 10 % (*Waiting for radiators to settle*), about 32 minutes.
+Forecasts continue meanwhile. Reloading the integration usually does not cause this
+wait, because the relay's last change is still known. *Ready* then needs 200
+accepted samples (about 17 hours) per room, including 30 with the relay ON and 30
+with it OFF, which can take a few days depending on how often the boiler runs.
+
 The **Heating MPC Status** entity's state is one of `waiting_for_sensors`,
 `learning`, `paused` (thermostat not in `heat`), `waiting_for_target`,
 `invalid_weights`, `ready`, `inputs_changed` or `prediction_error`. Proposed heat