Name malformed registry elements, parse ESPHOME_CCACHE_ENABLE strictly, require a package layout check

Registry version and file entries that are not dicts now raise the same
Unexpected-response error as the other shape guards instead of an
AttributeError traceback. install_package rejects an empty expect so
every install is layout-validated before the marker is written.
ESPHOME_CCACHE_ENABLE values outside 1/true/yes/on and 0/false/no/off
warn and are treated as unset instead of bool(str) flipping them to
enabled. The strip_win_long_path_prefix test moved next to the function
in test_framework_helpers, and a stale comment naming its old module is
fixed.

tests/unit_tests/test_framework_helpers.py

@@ -2091,3 +2091,37 @@ class TestGetProjectCxxCompileFlags:
     def test_empty_flags(self) -> None:
         with patch("esphome.core.CORE", _make_core_cxx(set())):
             assert get_project_cxx_compile_flags() == []
+
+
+@pytest.mark.parametrize(
+    ("platform", "input_path", "expected"),
+    [
+        # win32: drive-letter extended-length prefix is stripped
+        (
+            "win32",
+            "\\\\?\\C:\\Users\\jesse\\AppData\\Local\\ESPHome Builder\\python\\python.exe",
+            "C:\\Users\\jesse\\AppData\\Local\\ESPHome Builder\\python\\python.exe",
+        ),
+        # win32: UNC extended-length prefix is translated to a regular UNC path
+        (
+            "win32",
+            "\\\\?\\UNC\\server\\share\\python.exe",
+            "\\\\server\\share\\python.exe",
+        ),
+        # win32: paths without the prefix are returned unchanged
+        (
+            "win32",
+            "C:\\Users\\jesse\\AppData\\Local\\ESPHome Builder\\python\\python.exe",
+            "C:\\Users\\jesse\\AppData\\Local\\ESPHome Builder\\python\\python.exe",
+        ),
+        # non-win32: prefix is left alone (no-op)
+        ("linux", "\\\\?\\C:\\python.exe", "\\\\?\\C:\\python.exe"),
+        ("darwin", "/usr/bin/python3", "/usr/bin/python3"),
+    ],
+)
+def test_strip_win_long_path_prefix(
+    platform: str, input_path: str, expected: str
+) -> None:
+    r"""``\\?\`` and ``\\?\UNC\`` prefixes are stripped only on win32."""
+    with patch("esphome.framework_helpers.sys.platform", platform):
+        assert framework_helpers.strip_win_long_path_prefix(input_path) == expected