fix(distribution): refuse to replace a symlinked owned container

A user who points `profiles/x/skills` at a shared directory did so on
purpose. The merge path replaced such a symlink with a real directory
silently, discarding that configuration, where the base rmtree at least
failed loudly. Raise DistributionError naming the link instead; the
file->directory replacement stays because a stray file there is never
deliberate configuration.

`_remove_existing` now removes anything that lexists but is not a real
directory via unlink, so fifos and sockets no longer slip through.

Reviewer P1 on the original PR (symlink container must survive intact).

hermes_cli/profile_distribution.py

@@ -8,6 +8,7 @@ development before the first push).
 from __future__ import annotations
 
 import operator
+import os
 import re
 import shutil
 import subprocess
@@ -358,10 +359,11 @@ def _owned_entries(staged: Path, manifest: DistributionManifest):
 
 def _remove_existing(path: Path) -> None:
     """Remove one destination entry without following a destination symlink."""
-    if path.is_symlink() or path.is_file():
-        path.unlink()
-    elif path.is_dir():
+    if path.is_dir() and not path.is_symlink():
         shutil.rmtree(path)
+    elif os.path.lexists(path):
+        # Covers files, dangling/any symlinks, fifos and sockets alike.
+        path.unlink()
 
 
 def _replace_entry(src: Path, dest: Path) -> None:
@@ -377,12 +379,18 @@ def _replace_entry(src: Path, dest: Path) -> None:
 def _real_dir(base: Path, parts: Tuple[str, ...]) -> Path:
     """Return ``base/parts`` as a chain of real directories.
 
-    A user could have swapped any ancestor for a symlink or a file; writing through it
-    would land the payload outside the profile, so each is replaced by a real directory."""
+    A user could have swapped an ancestor for a file; writing through it is impossible,
+    so a file is replaced by a real directory. A symlinked ancestor is refused rather
+    than silently unlinked: it is deliberate user configuration (a shared skills dir,
+    say) and writing through it would land the payload outside the profile."""
     path = base
     for part in parts:
         path = path / part
-        if path.is_symlink() or (path.exists() and not path.is_dir()):
+        if path.is_symlink():
+            raise DistributionError(
+                f"{path} is a symlink; refusing to replace it — remove the link or point distribution_owned elsewhere"
+            )
+        if path.exists() and not path.is_dir():
             _remove_existing(path)
         path.mkdir(exist_ok=True)
     return path

tests/hermes_cli/test_profile_distribution.py

@@ -10,6 +10,7 @@ mocking git would just test the mock.
 
 from __future__ import annotations
 
+import shutil
 import sys
 from pathlib import Path
 
@@ -424,6 +425,28 @@ class TestUpdate:
         assert (plan.target_dir / "cron" / "mine.json").read_text() == '{"schedule": "* * * * *"}\n'
         assert (plan.target_dir / "cron" / "daily.json").read_text() == '{"schedule": "0 10 * * *"}\n'
 
+    def test_update_refuses_symlinked_owned_container(self, profile_env):
+        staged = _make_staging_dir(profile_env, "src")
+        plan = install_distribution(str(staged), name="link_safe")
+
+        shared = profile_env / "shared-skills"
+        shared.mkdir()
+        (shared / "mine" / "SKILL.md").parent.mkdir()
+        (shared / "mine" / "SKILL.md").write_text("shared skill\n")
+        before = sorted((p.relative_to(shared), p.read_bytes()) for p in shared.rglob("*") if p.is_file())
+
+        skills = plan.target_dir / "skills"
+        shutil.rmtree(skills)
+        _symlink_file_or_skip(skills, shared)
+        (staged / "skills" / "demo" / "SKILL.md").write_text("updated demo\n")
+
+        with pytest.raises(DistributionError, match="symlink"):
+            update_distribution("link_safe")
+
+        assert skills.is_symlink() and skills.resolve() == shared.resolve()
+        after = sorted((p.relative_to(shared), p.read_bytes()) for p in shared.rglob("*") if p.is_file())
+        assert after == before
+
     def test_update_preserves_user_data(self, profile_env):
         # 1. Build staging dir, install
         staged = _make_staging_dir(profile_env, "src")