fix(skills): ignore support docs in skill discovery

Support files under references/, templates/, assets/, and scripts/ are progressive-disclosure data loaded through skill_view(..., file_path=...). They should not be treated as standalone skills during discovery or collision checks.

This prevents archived skill packages or support markdown files inside a real skill from shadowing active skills with the same name while still allowing top-level categories named scripts/templates/assets/references.

Tests cover:
- pruning nested SKILL.md files inside skill support directories
- preserving support-named top-level categories
- avoiding skill_view collisions from support markdown
- keeping archived package SKILL.md files accessible only through file_path

tests/tools/test_skills_tool.py

@@ -1225,6 +1225,89 @@ class TestSkillViewCollisionDetection:
         assert result["success"] is True
         assert "LOCAL VERSION" in result["content"]
 
+    def test_support_markdown_does_not_collide_with_real_skill(self, tmp_path):
+        """Supporting reference docs named <skill>.md are not skills.
+
+        A real-world regression had creative/sketch/SKILL.md become
+        unloadable because another skill carried
+        references/styles/sketch.md. Support files are loaded via
+        skill_view(skill, file_path=...), not as bare skill names.
+        """
+        local_dir = tmp_path / "local"
+        external_dir = tmp_path / "external"
+        local_dir.mkdir()
+        external_dir.mkdir()
+
+        _make_skill(local_dir, "article-illustrator", category="creative")
+        support_file = (
+            local_dir
+            / "creative"
+            / "article-illustrator"
+            / "references"
+            / "styles"
+            / "sketch.md"
+        )
+        support_file.parent.mkdir(parents=True, exist_ok=True)
+        support_file.write_text("# Sketch style support doc\n")
+        _make_skill(local_dir, "sketch", category="creative", body="REAL SKETCH SKILL")
+
+        p1, p2 = self._patch_dirs(local_dir, [external_dir])
+        with p1, p2:
+            raw = skill_view("sketch")
+
+        result = json.loads(raw)
+        assert result["success"] is True
+        assert result["path"] == "creative/sketch/SKILL.md"
+        assert "REAL SKETCH SKILL" in result["content"]
+
+    def test_reference_package_skill_md_is_not_active_skill(self, tmp_path):
+        """Curator-preserved package SKILL.md files under references stay data.
+
+        Umbrella consolidations may preserve an old skill as
+        references/old-skill-package/SKILL.md. That package must not appear in
+        skills_list/system prompts and must not resolve as skill_view("old-skill").
+        The package can still be opened explicitly through the umbrella's
+        file_path progressive-disclosure channel.
+        """
+        local_dir = tmp_path / "local"
+        external_dir = tmp_path / "external"
+        local_dir.mkdir()
+        external_dir.mkdir()
+
+        _make_skill(local_dir, "umbrella", category="creative", body="UMBRELLA")
+        package = (
+            local_dir
+            / "creative"
+            / "umbrella"
+            / "references"
+            / "old-skill-package"
+        )
+        package.mkdir(parents=True, exist_ok=True)
+        (package / "SKILL.md").write_text(
+            "---\nname: old-skill\ndescription: Preserved old skill.\n---\n\nOLD BODY\n"
+        )
+
+        p1, p2 = self._patch_dirs(local_dir, [external_dir])
+        with p1, p2:
+            names = {skill["name"] for skill in _find_all_skills()}
+            old_raw = skill_view("old-skill")
+            direct_package_raw = skill_view("creative/umbrella/references/old-skill-package")
+            package_raw = skill_view(
+                "umbrella", file_path="references/old-skill-package/SKILL.md"
+            )
+
+        assert "umbrella" in names
+        assert "old-skill" not in names
+        old_result = json.loads(old_raw)
+        assert old_result["success"] is False
+        assert "not found" in old_result["error"]
+        direct_package_result = json.loads(direct_package_raw)
+        assert direct_package_result["success"] is False
+        assert "not found" in direct_package_result["error"]
+        package_result = json.loads(package_raw)
+        assert package_result["success"] is True
+        assert "OLD BODY" in package_result["content"]
+
     def test_external_skill_resolves_when_no_collision(self, tmp_path):
         """External-only skills still resolve normally when there's no
         local skill of the same name."""