[template] Surface value metadata on template entity forms

Add cv.with_visibility(schema, visibility, *keys) to re-mark a built
schema's fields, and use it so the template platforms promote the value
metadata their users define (device_class, unit_of_measurement, ...) onto
the visual editor's main form instead of the advanced disclosure. Pure UI
hints; validation and runtime are unchanged.

tests/component_tests/template/test_template_visibility.py

@@ -0,0 +1,76 @@
+"""The template platforms surface value-describing metadata on the main form.
+
+Hardware platforms get sensible defaults for unit/device_class/etc., so those
+fields fall through to the editor's advanced disclosure. A ``template`` entity
+has no such defaults -- the user is expected to define them -- so the template
+platforms pass ``visibility=cv.Visibility.UI`` to promote them onto the form.
+"""
+
+from __future__ import annotations
+
+import importlib
+
+import pytest
+
+import esphome.config_validation as cv
+
+
+def _markers(schema: cv.Schema) -> dict[str, object]:
+    s = schema
+    if hasattr(s, "validators"):
+        # cv.All -> the schema is the first validator.
+        s = s.validators[0]
+    return {str(k): k for k in s.schema}
+
+
+@pytest.mark.parametrize(
+    ("platform", "fields"),
+    [
+        (
+            "sensor",
+            [
+                "unit_of_measurement",
+                "accuracy_decimals",
+                "device_class",
+                "state_class",
+                "force_update",
+            ],
+        ),
+        ("binary_sensor", ["device_class"]),
+        ("switch", ["device_class"]),
+        ("cover", ["device_class"]),
+        ("button", ["device_class"]),
+        ("valve", ["device_class"]),
+        ("event", ["device_class"]),
+        ("text_sensor", ["device_class"]),
+        ("number", ["device_class", "unit_of_measurement"]),
+    ],
+)
+def test_template_metadata_is_ui(platform: str, fields: list[str]) -> None:
+    mod = importlib.import_module(f"esphome.components.template.{platform}")
+    markers = _markers(mod.CONFIG_SCHEMA)
+    for field in fields:
+        assert markers[field].visibility is cv.Visibility.UI, f"{platform}.{field}"
+
+
+def test_template_sensor_promotion_preserves_defaults() -> None:
+    """Promoting to UI must not drop the fields' defaults."""
+    from esphome.components.template.sensor import CONFIG_SCHEMA
+
+    markers = _markers(CONFIG_SCHEMA)
+    assert markers["accuracy_decimals"].default() == 1
+    assert markers["force_update"].default() is False
+
+
+def test_hardware_platform_metadata_not_promoted() -> None:
+    """Without ``visibility=`` the builders leave metadata unset.
+
+    Unset markers fall through to the consumer's ``Optional`` default of
+    advanced, so hardware platforms are unaffected by the template promotion.
+    """
+    from esphome.components import binary_sensor, sensor
+
+    hw_sensor = _markers(sensor.sensor_schema(device_class="temperature"))
+    assert hw_sensor["device_class"].visibility is None
+    hw_bs = _markers(binary_sensor.binary_sensor_schema(device_class="motion"))
+    assert hw_bs["device_class"].visibility is None