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/agent/test_skill_utils.py

@@ -6,6 +6,8 @@ from agent.skill_utils import (
     extract_skill_conditions,
     get_disabled_skill_names,
     get_external_skills_dirs,
+    is_excluded_skill_path,
+    is_skill_support_path,
     iter_skill_index_files,
     resolve_skill_config_values,
     skill_matches_platform,
@@ -166,6 +168,51 @@ def test_skill_config_raw_cache_invalidates_on_config_edit(tmp_path, monkeypatch
     os.utime(config_path, None)
 
     assert get_disabled_skill_names() == {"new-skill"}
+def test_iter_skill_index_files_prunes_skill_support_dirs(tmp_path):
+    """Archived package SKILL.md files under support dirs are not active skills."""
+    real = tmp_path / "umbrella"
+    real.mkdir()
+    (real / "SKILL.md").write_text("---\nname: umbrella\n---\n", encoding="utf-8")
+
+    package = real / "references" / "old-skill-package"
+    package.mkdir(parents=True)
+    (package / "SKILL.md").write_text("---\nname: old-skill\n---\n", encoding="utf-8")
+    (package / "DESCRIPTION.md").write_text(
+        "---\ndescription: archived package\n---\n", encoding="utf-8"
+    )
+
+    script_package = real / "scripts" / "helper-skill"
+    script_package.mkdir(parents=True)
+    (script_package / "SKILL.md").write_text("---\nname: helper\n---\n", encoding="utf-8")
+
+    found = list(iter_skill_index_files(tmp_path, "SKILL.md"))
+    desc_found = list(iter_skill_index_files(tmp_path, "DESCRIPTION.md"))
+
+    assert found == [real / "SKILL.md"]
+    assert desc_found == []
+    assert is_skill_support_path(package / "SKILL.md") is True
+    assert is_excluded_skill_path(package / "SKILL.md") is True
+
+
+def test_iter_skill_index_files_keeps_support_named_categories(tmp_path):
+    """A category named scripts/templates/assets/references is still valid."""
+    scripts_skill = tmp_path / "scripts" / "bash-helper"
+    scripts_skill.mkdir(parents=True)
+    (scripts_skill / "SKILL.md").write_text(
+        "---\nname: bash-helper\n---\n", encoding="utf-8"
+    )
+
+    templates_skill = tmp_path / "templates" / "deck-template"
+    templates_skill.mkdir(parents=True)
+    (templates_skill / "SKILL.md").write_text(
+        "---\nname: deck-template\n---\n", encoding="utf-8"
+    )
+
+    found = list(iter_skill_index_files(tmp_path, "SKILL.md"))
+
+    assert found == [scripts_skill / "SKILL.md", templates_skill / "SKILL.md"]
+    assert is_skill_support_path(scripts_skill / "SKILL.md") is False
+    assert is_excluded_skill_path(scripts_skill / "SKILL.md") is False
 
 
 # ── skill_matches_platform on Termux ──────────────────────────────────────