Layer 3: Templates as pure data, weather template, .anvilignore refresh system

Templates are now composed declaratively via template.toml -- no Rust code
changes needed to add new templates. The weather station is the first
composed template, demonstrating the full pattern.

Template engine:
- Composed templates declare base, required libraries, and per-board pins
- Overlay mechanism replaces base files (app, sketch, tests) cleanly
- Generic orchestration: extract base, apply overlay, install libs, assign pins
- Template name tracked in .anvil.toml for refresh awareness

Weather template (--template weather):
- WeatherApp with 2-second polling, C/F conversion, serial output
- TMP36 driver: TempSensor interface, Tmp36 impl, Tmp36Mock, Tmp36Sim
- Managed example tests in test_weather.cpp (unit + system)
- Minimal student starters in test_unit.cpp and test_system.cpp
- Per-board pin defaults (A0 for uno, A0 for mega, A0 for nano)

.anvilignore system:
- Glob pattern matching (*, ?) with comments and backslash normalization
- Default patterns protect student tests, app code, sketch, config
- anvil refresh --force respects .anvilignore
- anvil refresh --force --file <path> overrides ignore for one file
- anvil refresh --ignore/--unignore manages patterns from CLI
- Missing managed files always recreated even without --force
- .anvilignore itself is in NEVER_REFRESH (cannot be overwritten)

Refresh rewrite:
- Discovers all template-produced files dynamically (no hardcoded list)
- Extracts fresh template + libraries into temp dir for byte comparison
- Config template field drives which files are managed
- Separated missing-file creation from changed-file updates

428 tests passing on Windows MSVC, 0 warnings.

templates/weather/test/test_system.cpp.tmpl

@@ -0,0 +1,28 @@
+/*
+ * test_system.cpp -- Your system tests go here.
+ *
+ * This file is YOURS. Anvil will never overwrite it.
+ * The weather station example tests are in test_weather.cpp.
+ *
+ * System tests use SimHal and Tmp36Sim to exercise real application
+ * logic against simulated hardware. See test_weather.cpp for examples.
+ */
+
+#include <gtest/gtest.h>
+
+#include "mock_arduino.h"
+#include "hal.h"
+#include "sim_hal.h"
+#include "tmp36_sim.h"
+#include "{{PROJECT_NAME}}_app.h"
+
+// Example: add your own system tests below
+// TEST(MySystemTests, DescribeWhatItTests) {
+//     mock_arduino_reset();
+//     SimHal sim;
+//     Tmp36Sim sensor(25.0f, 0.5f);
+//
+//     WeatherApp app(&sim, &sensor);
+//     app.begin();
+//     // ... your test logic ...
+// }

templates/weather/test/test_unit.cpp.tmpl

@@ -0,0 +1,30 @@
+/*
+ * test_unit.cpp -- Your unit tests go here.
+ *
+ * This file is YOURS. Anvil will never overwrite it.
+ * The weather station example tests are in test_weather.cpp.
+ *
+ * Unit tests use MockHal and Tmp36Mock to verify exact behavior
+ * without real hardware. See test_weather.cpp for examples.
+ */
+
+#include <gtest/gtest.h>
+#include <gmock/gmock.h>
+
+#include "hal.h"
+#include "mock_hal.h"
+#include "tmp36_mock.h"
+#include "{{PROJECT_NAME}}_app.h"
+
+using ::testing::_;
+using ::testing::AnyNumber;
+using ::testing::Return;
+
+// Example: add your own tests below
+// TEST(MyTests, DescribeWhatItTests) {
+//     ::testing::NiceMock<MockHal> mock;
+//     Tmp36Mock sensor;
+//     sensor.setTemperature(25.0f);
+//
+//     // ... your test logic ...
+// }

templates/weather/test/test_weather.cpp.tmpl

@@ -0,0 +1,250 @@
+/*
+ * test_weather.cpp -- Weather station example tests.
+ *
+ * THIS FILE IS MANAGED BY ANVIL and will be updated by `anvil refresh`.
+ * Do not edit -- put your own tests in test_unit.cpp and test_system.cpp.
+ */
+
+#include <gtest/gtest.h>
+#include <gmock/gmock.h>
+
+#include "mock_arduino.h"
+#include "hal.h"
+#include "mock_hal.h"
+#include "sim_hal.h"
+#include "tmp36_mock.h"
+#include "tmp36_sim.h"
+#include "{{PROJECT_NAME}}_app.h"
+
+using ::testing::_;
+using ::testing::AnyNumber;
+using ::testing::Return;
+using ::testing::HasSubstr;
+
+// ============================================================================
+// Unit Tests -- verify WeatherApp behavior with mock sensor
+// ============================================================================
+
+class WeatherUnitTest : public ::testing::Test {
+protected:
+    void SetUp() override {
+        ON_CALL(mock_, millis()).WillByDefault(Return(0));
+        EXPECT_CALL(mock_, serialBegin(_)).Times(AnyNumber());
+        EXPECT_CALL(mock_, serialPrint(_)).Times(AnyNumber());
+        EXPECT_CALL(mock_, serialPrintln(_)).Times(AnyNumber());
+        EXPECT_CALL(mock_, millis()).Times(AnyNumber());
+    }
+
+    ::testing::NiceMock<MockHal> mock_;
+    Tmp36Mock sensor_;
+};
+
+TEST_F(WeatherUnitTest, BeginPrintsStartupMessage) {
+    WeatherApp app(&mock_, &sensor_);
+
+    EXPECT_CALL(mock_, serialBegin(115200)).Times(1);
+    EXPECT_CALL(mock_, serialPrintln(HasSubstr("WeatherApp started"))).Times(1);
+
+    app.begin();
+}
+
+TEST_F(WeatherUnitTest, BeginTakesInitialReading) {
+    sensor_.setTemperature(25.0f);
+    WeatherApp app(&mock_, &sensor_);
+    app.begin();
+
+    EXPECT_EQ(app.readCount(), 1);
+    EXPECT_NEAR(app.lastCelsius(), 25.0f, 0.1f);
+}
+
+TEST_F(WeatherUnitTest, ReadsAfterInterval) {
+    sensor_.setTemperature(20.0f);
+    WeatherApp app(&mock_, &sensor_);
+
+    ON_CALL(mock_, millis()).WillByDefault(Return(0));
+    app.begin();
+    EXPECT_EQ(app.readCount(), 1);
+
+    // Not enough time yet
+    ON_CALL(mock_, millis()).WillByDefault(Return(1999));
+    app.update();
+    EXPECT_EQ(app.readCount(), 1);
+
+    // Now 2 seconds have passed
+    ON_CALL(mock_, millis()).WillByDefault(Return(2000));
+    app.update();
+    EXPECT_EQ(app.readCount(), 2);
+}
+
+TEST_F(WeatherUnitTest, DoesNotReadTooEarly) {
+    sensor_.setTemperature(22.0f);
+    WeatherApp app(&mock_, &sensor_);
+
+    ON_CALL(mock_, millis()).WillByDefault(Return(0));
+    app.begin();
+
+    ON_CALL(mock_, millis()).WillByDefault(Return(1500));
+    app.update();
+
+    EXPECT_EQ(app.readCount(), 1);
+}
+
+TEST_F(WeatherUnitTest, CelsiusToFahrenheitConversion) {
+    sensor_.setTemperature(0.0f);
+    WeatherApp app(&mock_, &sensor_);
+    app.begin();
+
+    EXPECT_NEAR(app.lastCelsius(), 0.0f, 0.1f);
+    EXPECT_NEAR(app.lastFahrenheit(), 32.0f, 0.1f);
+}
+
+TEST_F(WeatherUnitTest, BoilingPoint) {
+    sensor_.setTemperature(100.0f);
+    WeatherApp app(&mock_, &sensor_);
+    app.begin();
+
+    EXPECT_NEAR(app.lastCelsius(), 100.0f, 0.1f);
+    EXPECT_NEAR(app.lastFahrenheit(), 212.0f, 0.1f);
+}
+
+TEST_F(WeatherUnitTest, NegativeTemperature) {
+    sensor_.setTemperature(-10.0f);
+    WeatherApp app(&mock_, &sensor_);
+    app.begin();
+
+    EXPECT_NEAR(app.lastCelsius(), -10.0f, 0.1f);
+    EXPECT_NEAR(app.lastFahrenheit(), 14.0f, 0.1f);
+}
+
+TEST_F(WeatherUnitTest, PrintsTemperatureOnRead) {
+    sensor_.setTemperature(25.0f);
+    WeatherApp app(&mock_, &sensor_);
+
+    EXPECT_CALL(mock_, serialPrint(HasSubstr("Temperature: "))).Times(1);
+    EXPECT_CALL(mock_, serialPrintln(HasSubstr(" F)"))).Times(1);
+
+    app.begin();
+}
+
+TEST_F(WeatherUnitTest, MultipleReadingsTrackNewTemperature) {
+    WeatherApp app(&mock_, &sensor_);
+
+    sensor_.setTemperature(20.0f);
+    ON_CALL(mock_, millis()).WillByDefault(Return(0));
+    app.begin();
+    EXPECT_NEAR(app.lastCelsius(), 20.0f, 0.1f);
+
+    sensor_.setTemperature(30.0f);
+    ON_CALL(mock_, millis()).WillByDefault(Return(2000));
+    app.update();
+    EXPECT_NEAR(app.lastCelsius(), 30.0f, 0.1f);
+    EXPECT_EQ(app.readCount(), 2);
+}
+
+// ============================================================================
+// System Tests -- exercise WeatherApp with simulated sensor and hardware
+// ============================================================================
+
+class WeatherSystemTest : public ::testing::Test {
+protected:
+    void SetUp() override {
+        mock_arduino_reset();
+        sim_.setMillis(0);
+    }
+
+    SimHal sim_;
+    Tmp36Sim sensor_{25.0f};  // 25 C base temperature
+};
+
+TEST_F(WeatherSystemTest, StartsAndPrintsToSerial) {
+    WeatherApp app(&sim_, &sensor_);
+    app.begin();
+
+    std::string output = sim_.serialOutput();
+    EXPECT_NE(output.find("WeatherApp started"), std::string::npos);
+    EXPECT_NE(output.find("Temperature:"), std::string::npos);
+}
+
+TEST_F(WeatherSystemTest, InitialReadingIsReasonable) {
+    Tmp36Sim exact_sensor(25.0f, 0.0f);  // zero noise
+    WeatherApp app(&sim_, &exact_sensor);
+    app.begin();
+
+    EXPECT_NEAR(app.lastCelsius(), 25.0f, 1.0f);
+    EXPECT_EQ(app.readCount(), 1);
+}
+
+TEST_F(WeatherSystemTest, ReadsAtTwoSecondIntervals) {
+    WeatherApp app(&sim_, &sensor_);
+    app.begin();
+    EXPECT_EQ(app.readCount(), 1);
+
+    // 1 second -- no new reading
+    sim_.advanceMillis(1000);
+    app.update();
+    EXPECT_EQ(app.readCount(), 1);
+
+    // 2 seconds -- new reading
+    sim_.advanceMillis(1000);
+    app.update();
+    EXPECT_EQ(app.readCount(), 2);
+
+    // 4 seconds -- another reading
+    sim_.advanceMillis(2000);
+    app.update();
+    EXPECT_EQ(app.readCount(), 3);
+}
+
+TEST_F(WeatherSystemTest, FiveMinuteRun) {
+    WeatherApp app(&sim_, &sensor_);
+    app.begin();
+
+    // Run 5 minutes at 100ms resolution
+    for (int i = 0; i < 3000; ++i) {
+        sim_.advanceMillis(100);
+        app.update();
+    }
+
+    // 5 minutes = 300 seconds / 2 second interval = 150 readings + 1 initial
+    EXPECT_EQ(app.readCount(), 151);
+}
+
+TEST_F(WeatherSystemTest, TemperatureChangeMidRun) {
+    Tmp36Sim sensor(20.0f, 0.0f);  // start at 20 C, no noise
+    WeatherApp app(&sim_, &sensor);
+    app.begin();
+
+    EXPECT_NEAR(app.lastCelsius(), 20.0f, 1.0f);
+
+    // Change temperature and wait for next reading
+    sensor.setBaseTemperature(35.0f);
+    sim_.advanceMillis(2000);
+    app.update();
+
+    EXPECT_NEAR(app.lastCelsius(), 35.0f, 1.0f);
+}
+
+TEST_F(WeatherSystemTest, SerialOutputContainsFahrenheit) {
+    Tmp36Sim exact_sensor(0.0f, 0.0f);  // 0 C = 32 F
+    WeatherApp app(&sim_, &exact_sensor);
+    app.begin();
+
+    std::string output = sim_.serialOutput();
+    EXPECT_NE(output.find("32"), std::string::npos)
+        << "Should contain 32 F for 0 C: " << output;
+}
+
+TEST_F(WeatherSystemTest, NoisyReadingsStayInRange) {
+    Tmp36Sim noisy_sensor(25.0f, 2.0f);  // +/- 2 C noise
+    noisy_sensor.setSeed(42);
+    WeatherApp app(&sim_, &noisy_sensor);
+
+    for (int i = 0; i < 20; ++i) {
+        sim_.setMillis(i * 2000);
+        if (i == 0) app.begin(); else app.update();
+
+        float c = app.lastCelsius();
+        EXPECT_GE(c, 20.0f) << "Reading " << i << " too low: " << c;
+        EXPECT_LE(c, 30.0f) << "Reading " << i << " too high: " << c;
+    }
+}