ship the references sidecar for gemini installs

gemini has no _PLATFORM_CONFIG entry and installs claude's skill.md body
verbatim. Since #1121 that body is the lean progressive core that links to
references/, but _packaged_skill_refs_dir returned None for gemini, so the
install laid down a SKILL.md with 8 dead reference pointers. Resolve gemini
to the claude references bundle (the same body it already ships) and guard
it in test_claude_twins_ride_the_claude_bundle.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

graphify/__main__.py

@@ -171,7 +171,13 @@ def _packaged_skill_refs_dir(platform_name: str) -> Path | None:
     A platform opts into progressive disclosure by setting ``skill_refs`` in its
     ``_PLATFORM_CONFIG`` entry. The value names a bundle under
     ``graphify/skills/<bundle>/references/``. Reuse keys (e.g. trae-cn) point at
-    their twin's bundle. ``gemini`` has no config entry and is never progressive.
+    their twin's bundle.
+
+    ``gemini`` has no ``_PLATFORM_CONFIG`` entry: it installs claude's
+    ``skill.md`` body verbatim (see ``_copy_skill_file``). Since that body is the
+    lean progressive core that links to ``references/``, gemini needs claude's
+    references/ sidecar too, or its SKILL.md ships with dead pointers. So gemini
+    resolves to the claude bundle rather than opting out.
 
     Bundles ship one platform-group at a time. A host whose bundle directory
     ``graphify/skills/<bundle>/`` is not in this build has not gone progressive
@@ -182,8 +188,9 @@ def _packaged_skill_refs_dir(platform_name: str) -> Path | None:
     the empty-sidecar regression the wheel-content test also guards).
     """
     if platform_name == "gemini":
-        return None
-    bundle = _PLATFORM_CONFIG[platform_name].get("skill_refs")
+        bundle = "claude"
+    else:
+        bundle = _PLATFORM_CONFIG[platform_name].get("skill_refs")
     if not bundle:
         return None
     bundle_dir = Path(__file__).parent / "skills" / bundle

tests/test_install_references.py

@@ -269,8 +269,13 @@ def test_claude_install_ships_lean_core_and_references(tmp_path):
 
 
 def test_claude_twins_ride_the_claude_bundle(tmp_path):
-    """antigravity and kimi reuse claude's split bundle, so they go progressive too."""
-    for platform in ("antigravity", "kimi"):
+    """antigravity and kimi reuse claude's split bundle, so they go progressive too.
+
+    gemini has no _PLATFORM_CONFIG entry but installs claude's skill.md body
+    verbatim; that body is the lean progressive core, so gemini must ride the
+    claude references bundle as well or it ships a SKILL.md with dead pointers.
+    """
+    for platform in ("antigravity", "kimi", "gemini"):
         refs_src = mainmod._packaged_skill_refs_dir(platform)
         assert refs_src is not None
         assert refs_src == PKG_DIR / "skills" / "claude" / "references"