fix(espidf): include non-utility subdirs for libs without src/ layout

The _should_include filter inside _merge_arduino_libs_to_component
rejected every subdirectory of a library except 'utility/' when the
library lacked a src/ layout. That blocked legitimate header dirs like
Adafruit_GFX_Library/Fonts/, breaking compiles that use any GxEPD2
example with a custom font (#include <Fonts/FreeMonoBold12pt7b.h>).

The earlier filter at the top of the function already excludes
docs/examples/tests/etc. via excluded_dirs, so anything that survives
that check is presumed to be buildable source. Letting all remaining
subdirs through restores Fonts/, gfxfont/, and similar conventional
auxiliary header directories that Adafruit-style libs rely on.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/app/services/espidf_compiler.py

@@ -473,7 +473,11 @@ class ESPIDFCompiler:
                         return False
                     if has_src_layout:
                         return parts[0] == 'src' or len(parts) == 1
-                    return len(parts) == 1 or parts[0].lower() == 'utility'
+                    # Non-src-layout libs (Adafruit_GFX, etc.) keep auxiliary
+                    # headers in subdirs like Fonts/ or gfxfont/. Anything not
+                    # already excluded (docs/examples/tests handled above) is
+                    # presumed to be buildable source.
+                    return True
 
                 for f in lib_root.rglob('*'):
                     if not f.is_file():