test(ui): Add test_parameter_metadata.cpp

Split from monolithic test_parameter_validation.cpp into focused
metadata validation tests covering:
- Range boundary checks (min, max, exact boundaries)
- Extreme limit validation (numeric_limits)
- Integer vs double type validation
- Builder API: name, description, required, typical, units, category
- format_info() output verification for user-facing summaries

Improves test isolation and speeds discovery under single-invocation
runner. Part of UI parameter validation refactoring to align with
"laboratory, not fortress" philosophy.

Author: ahojukka5

tests/unit/ui/test_parameter_metadata.cpp

@@ -0,0 +1,106 @@
+// SPDX-FileCopyrightText: 2025 VTT Technical Research Centre of Finland Ltd
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+#include "openpfc/ui/parameter_metadata.hpp"
+#include <catch2/catch_all.hpp>
+
+using namespace pfc::ui;
+
+TEST_CASE("ParameterMetadata double validation", "[parameter_metadata][unit]") {
+  SECTION("Valid value within range") {
+    auto meta = ParameterMetadata<double>::builder()
+                    .name("temperature")
+                    .description("Temperature in Kelvin")
+                    .min(0.0)
+                    .max(10000.0)
+                    .build();
+
+    auto error = meta.validate(3300.0);
+    REQUIRE_FALSE(error.has_value());
+  }
+
+  SECTION("Value below minimum") {
+    auto meta =
+        ParameterMetadata<double>::builder().name("temperature").min(0.0).build();
+
+    auto error = meta.validate(-100.0);
+    REQUIRE(error.has_value());
+    REQUIRE(error->find("below minimum") != std::string::npos);
+    REQUIRE(error->find("temperature") != std::string::npos);
+  }
+
+  SECTION("Value above maximum") {
+    auto meta = ParameterMetadata<double>::builder()
+                    .name("temperature")
+                    .max(10000.0)
+                    .build();
+
+    auto error = meta.validate(15000.0);
+    REQUIRE(error.has_value());
+    REQUIRE(error->find("exceeds maximum") != std::string::npos);
+    REQUIRE(error->find("temperature") != std::string::npos);
+  }
+
+  SECTION("Value exactly at boundary") {
+    auto meta = ParameterMetadata<double>::builder()
+                    .name("density")
+                    .range(-1.0, 0.0)
+                    .build();
+
+    REQUIRE_FALSE(meta.validate(-1.0).has_value());
+    REQUIRE_FALSE(meta.validate(0.0).has_value());
+    REQUIRE(meta.validate(-1.1).has_value());
+    REQUIRE(meta.validate(0.1).has_value());
+  }
+
+  SECTION("Extreme boundary values") {
+    auto meta = ParameterMetadata<double>::builder()
+                    .name("extreme")
+                    .range(std::numeric_limits<double>::lowest(),
+                           std::numeric_limits<double>::max())
+                    .build();
+
+    REQUIRE_FALSE(meta.validate(std::numeric_limits<double>::lowest()).has_value());
+    REQUIRE_FALSE(meta.validate(std::numeric_limits<double>::max()).has_value());
+    REQUIRE_FALSE(meta.validate(0.0).has_value());
+  }
+}
+
+TEST_CASE("ParameterMetadata integer validation", "[parameter_metadata][unit]") {
+  SECTION("Valid integer value") {
+    auto meta =
+        ParameterMetadata<int>::builder().name("num_steps").range(1, 1000).build();
+
+    REQUIRE_FALSE(meta.validate(100).has_value());
+  }
+
+  SECTION("Integer out of range") {
+    auto meta =
+        ParameterMetadata<int>::builder().name("num_steps").range(1, 1000).build();
+
+    REQUIRE(meta.validate(0).has_value());
+    REQUIRE(meta.validate(1001).has_value());
+  }
+}
+
+TEST_CASE("ParameterMetadata format_info", "[parameter_metadata][unit]") {
+  auto meta = ParameterMetadata<double>::builder()
+                  .name("temperature")
+                  .description("Effective temperature")
+                  .required(true)
+                  .range(0.0, 10000.0)
+                  .typical(3300.0)
+                  .units("K")
+                  .category("Thermodynamics")
+                  .build();
+
+  std::string info = meta.format_info();
+
+  REQUIRE(info.find("temperature") != std::string::npos);
+  REQUIRE(info.find("Effective temperature") != std::string::npos);
+  REQUIRE(info.find("K") != std::string::npos);
+  REQUIRE(info.find("0") != std::string::npos);
+  REQUIRE(info.find("10000") != std::string::npos);
+  REQUIRE(info.find("3300") != std::string::npos);
+  REQUIRE(info.find("yes") != std::string::npos);
+}