feat: add font list command, fix cligen for complex constructors

- font list: uses ASystemFontIterator to enumerate system fonts.
  Works from headless CLI (verified on Pixel 8a: lists Roboto etc.)
- font match: AFontMatcher_match crashes in libminikin (null
  FontCollection) — this is a minikin-internal issue, not our code.
  ASystemFontIterator works fine from the same process.
- cligen: skip params with unsupported types instead of generating
  invalid flag code. Treat constructors with non-CLI params as
  "requires external context".
- Added system_fonts.h to font manifest for ASystemFontIterator.
- Added check-no-capi CI step.

Author: xaionaro@dx.center

capi/font/cgo_helpers.go

@@ -2,6 +2,7 @@
 
 #include "android/font.h"
 #include "android/font_matcher.h"
+#include "android/system_fonts.h"
 #include <stdlib.h>
 #pragma once
 

capi/font/cgo_helpers.h

@@ -2,6 +2,6 @@ GENERATOR:
   PackageName: font
   PackageDescription: "Raw CGo bindings for Android Font"
   PackageLicense: "Apache-2.0"
-  Includes: ["android/font.h", "android/font_matcher.h"]
+  Includes: ["android/font.h", "android/font_matcher.h", "android/system_fonts.h"]
   FlagGroups:
     - {name: LDFLAGS, flags: [-landroid]}