fix(skills): a SKILL.md link above the skill directory no longer makes the skill uninstallable

`_referenced_support_paths` returned None (bundle rejected) when a same-directory
markdown link started with `..`. Such a link (`../../tools/REGISTRY.md` in a
multi-skill repo) is prose: it is never fetched and never becomes a bundle path,
so the refusal protected nothing while every skill that links a sibling doc failed
with "files no longer exist upstream" / "Could not fetch from any source" — the
reporter's five marketingskills names, which curl fetched fine. Skip the link with
a warning instead; support-dir traversal (`references/../x`) is still rejected
because that path IS written into the bundle.

tests/tools/test_skill_bundle_provenance.py

@@ -134,15 +134,23 @@ def test_same_dir_linked_siblings_are_fetched(served_repo, monkeypatch):
     assert "README.md" not in bundle.files
 
 
-def test_same_dir_traversal_link_is_rejected(monkeypatch):
-    source = UrlSource()
-    skill = (
-        "---\nname: bad\ndescription: bad\n---\n"
-        "[bad](./../outside-secret.md)\n"
-    )
-    monkeypatch.setattr(source, "_fetch_text", lambda _url: skill)
+def test_same_dir_link_outside_skill_dir_is_skipped_not_fatal(served_repo, monkeypatch):
+    """A repo-relative link above the skill directory is prose, not a bundle path (#115171).
 
-    assert source.fetch("https://example.com/bad/SKILL.md") is None
+    Nothing is fetched for it, so it must not reject the bundle: the skill installs with
+    SKILL.md and its real siblings, and the outside link is simply left dangling.
+    """
+    repo, url = served_repo
+    (repo / "DEFS.md").write_text("defs\n")
+    (repo / "SKILL.md").write_text(SKILL_MD + "[registry](../../tools/REGISTRY.md) and [defs](./DEFS.md)\n")
+    monkeypatch.setattr("tools.skills_hub.is_safe_url", lambda _url: True)
+    monkeypatch.setattr("tools.skills_hub.check_website_access", lambda _url: None)
+
+    bundle = UrlSource().fetch(url)
+
+    assert bundle is not None
+    assert "DEFS.md" in bundle.files
+    assert not any(".." in name for name in bundle.files)
 
 
 def test_same_dir_link_without_extension_is_ignored(monkeypatch):

tools/skills_hub_models.py

@@ -312,7 +312,13 @@ def _referenced_support_paths(skill_md: str) -> Optional[set[str]]:
         if not name or "://" in raw or raw.startswith(("mailto:", "#", "/")):
             continue
         if name.startswith(".."):
-            return None
+            # A repo-relative link to a doc outside the skill directory (``../../tools/REGISTRY.md``
+            # in a multi-skill repo) is prose, never a bundle path: nothing is fetched or written for
+            # it, so refusing the whole bundle protected nothing and made every skill that links a
+            # sibling doc uninstallable with a misleading "files no longer exist upstream" (#115171).
+            # The link is left dangling in the installed copy, like an absent support file.
+            logger.warning("SKILL.md links outside the skill directory; installing without it: %s", raw)
+            continue
         # Only unambiguous file links: an extension, no internal slash, never SKILL.md itself (casefolded —
         # a ``skill.md`` entry would collide with the bundle root on macOS/Windows; skipped, not merged).
         if ("/" in name or name.casefold() == "skill.md" or "." not in name.lstrip(".")