[core] Don't emit IIFE for comment-only chunks

Some components (sha256, async_tcp, network, empty text_sensor:, etc.)
emit only a ComponentMarker plus config-dump comments and no actual
C++ statements. Wrapping those in a `[]() { ... }();` IIFE is pure
clutter in the generated main.cpp — the IIFE has no body.

When _wrap_in_iifes sees a chunk whose lines are all // comments,
emit them verbatim instead of wrapping. Peak stack and flash are
unchanged on apollo and neargaragedoor since GCC was already
eliding the empty IIFEs; this just makes the generated code read
cleanly to humans.

tests/unit_tests/test_core.py

@@ -934,6 +934,13 @@ def test_wrap_in_iifes_unbalanced_braces_fall_through() -> None:
     assert [line for line in result if line in lines] == lines
 
 
+def test_wrap_in_iifes_skips_comment_only_chunks() -> None:
+    # Components that emit only a ComponentMarker + config dump (no C++
+    # statements) should not be wrapped in an empty IIFE.
+    lines = ["// === sha256 ===", "// sha256:", "//   {}"]
+    assert core._wrap_in_iifes(lines, max_statements=50) == lines
+
+
 def test_cpp_main_section_no_components_emits_flat() -> None:
     target = core.EsphomeCore()
     target.main_statements = [RawStatement("a();"), RawStatement("b();")]