fix: create skills directory on demand during extension/preset install (#2711)

* fix: create skills directory on demand during extension/preset install

_get_skills_dir() in both extensions.py and presets.py returned None
when the skills directory did not yet exist on disk, even though skills
were enabled in init-options. This caused extension skill registration
to silently produce an empty registered_skills list and skip writing
SKILL.md files.

Replace the is_dir() bail-out with mkdir(parents=True, exist_ok=True)
so the directory is created on demand when ai_skills is enabled.

Update the existing test expectation and add a parametrized regression
test (claude + codex) that installs an extension before the skills
directory exists and asserts SKILL.md files and registry entries are
created.

Fixes #2682

* test: assert skills dir is NOT created when skills are disabled

Strengthen negative tests to verify _get_skills_dir does not create the
directory on disk when ai_skills is false or init-options.json is absent.

* fix: add symlink/containment check and preserve Kimi existence gate

Address PR review feedback:

- Use _ensure_safe_shared_directory() instead of raw mkdir() to prevent
  symlink-following writes outside the project root.
- Restore the is_dir() existence gate for the Kimi native-skills
  fallback (ai_skills=false): only create the directory on demand when
  ai_skills is explicitly enabled.
- Update docstrings to reflect the on-demand vs existence-gate behavior.
- Reuse resolve_skills_dir helper in tests instead of manually
  reconstructing paths from AGENT_CONFIG.

* refactor: extract resolve_active_skills_dir shared helper

Deduplicate the _get_skills_dir logic that was nearly identical in
ExtensionManager and PresetManager into a single module-level
resolve_active_skills_dir() function in __init__.py.

The shared helper wraps _ensure_safe_shared_directory errors with
skills-specific messages so users see 'agent skills directory' instead
of 'shared infrastructure directory' in error output.

Both class methods now delegate to the shared helper.

* fix: preserve original error reason in skills dir safety check

Include the original exception message from _ensure_safe_shared_directory
in the re-raised ValueError so the user sees the specific reason (symlink,
not-a-directory, path escape, etc.) instead of a generic message.

* fix: handle skills dir safety errors gracefully during install

Catch ValueError/OSError from _get_skills_dir() inside
_register_extension_skills() so a symlink or permission error logs a
warning and returns [] instead of aborting mid-install and leaving a
partially-installed extension without a registry entry.

Also document OSError in resolve_active_skills_dir() docstring.

* fix: catch errors in _get_skills_dir and use _print_cli_warning

Move the ValueError/OSError catch from _register_extension_skills into
_get_skills_dir itself so all callers (install, uninstall, reconcile)
are protected from unsafe-path exceptions.

Replace logging.getLogger().warning with _print_cli_warning for
consistent Rich-formatted user output.

* fix: use context-aware error messages for skills directory safety

Add a 'context' parameter to _ensure_safe_shared_directory (defaults to
'shared infrastructure directory' for backward compat). The skills dir
caller passes context='agent skills directory' so error messages say
e.g. 'Refusing to use symlinked agent skills directory' instead of
'Refusing to use symlinked shared infrastructure directory'.

Simplify resolve_active_skills_dir by removing the now-unnecessary
try/except wrapper.

* fix: validate Kimi native-skills directory for symlink/containment

The Kimi fallback path (ai_skills=false) used is_dir() which follows
symlinks, so a symlinked .kimi/skills could cause writes outside the
project root. Now validates with _ensure_safe_shared_directory(create=
False) before returning the directory.

src/specify_cli/__init__.py

@@ -317,6 +317,57 @@ def _get_skills_dir(project_path: Path, selected_ai: str) -> Path:
     return project_path / ".agents" / "skills"
 
 
+def resolve_active_skills_dir(project_root: Path) -> Path | None:
+    """Return the active skills directory, creating it on demand when enabled.
+
+    Reads ``.specify/init-options.json`` to determine whether skills are
+    enabled and which agent was selected.  When ``ai_skills`` is true the
+    directory is created safely (symlink/containment checks); when false
+    only Kimi's native-skills fallback is honoured (directory must already
+    exist).
+
+    Returns:
+        The skills directory ``Path``, or ``None`` if skills are not active.
+
+    Raises:
+        ValueError: If the resolved skills path escapes the project root,
+            a parent component is a symlink, or a path component exists
+            but is not a directory.
+        OSError: If the directory cannot be created (e.g. permission denied).
+    """
+    from .shared_infra import _ensure_safe_shared_directory
+
+    opts = load_init_options(project_root)
+    if not isinstance(opts, dict):
+        opts = {}
+
+    agent = opts.get("ai")
+    if not isinstance(agent, str) or not agent:
+        return None
+
+    ai_skills_enabled = bool(opts.get("ai_skills"))
+    if not ai_skills_enabled and agent != "kimi":
+        return None
+
+    skills_dir = _get_skills_dir(project_root, agent)
+
+    if not ai_skills_enabled:
+        # Kimi native-skills fallback: use the directory only if it exists.
+        if not skills_dir.is_dir():
+            return None
+        _ensure_safe_shared_directory(
+            project_root, skills_dir,
+            create=False, context="agent skills directory",
+        )
+        return skills_dir
+
+    # ai_skills is explicitly enabled — create the directory safely.
+    _ensure_safe_shared_directory(
+        project_root, skills_dir, context="agent skills directory",
+    )
+    return skills_dir
+
+
 def _cli_error_detail(exc: BaseException) -> str:
     """Return a compact one-line exception detail for CLI output."""
     detail = str(exc).replace("\n", " ").strip()