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/shared_infra.py

@@ -88,7 +88,13 @@ def _shared_relative_path(project_path: Path, dest: Path) -> Path:
     return rel
 
 
-def _ensure_safe_shared_directory(project_path: Path, directory: Path, *, create: bool = True) -> None:
+def _ensure_safe_shared_directory(
+    project_path: Path,
+    directory: Path,
+    *,
+    create: bool = True,
+    context: str = "shared infrastructure directory",
+) -> None:
     """Create a shared infra directory without following symlinked parents."""
     root = project_path.resolve()
     rel = _shared_relative_path(project_path, directory)
@@ -98,24 +104,24 @@ def _ensure_safe_shared_directory(project_path: Path, directory: Path, *, create
         current = current / part
         label = _shared_destination_label(project_path, current)
         if current.is_symlink():
-            raise SymlinkedSharedPathError(f"Refusing to use symlinked shared infrastructure directory: {label}")
+            raise SymlinkedSharedPathError(f"Refusing to use symlinked {context}: {label}")
         if current.exists():
             if not current.is_dir():
-                raise ValueError(f"Shared infrastructure directory path is not a directory: {label}")
+                raise ValueError(f"{context.capitalize()} path is not a directory: {label}")
             try:
                 current.resolve().relative_to(root)
             except (OSError, ValueError):
-                raise ValueError(f"Shared infrastructure directory escapes project root: {label}") from None
+                raise ValueError(f"{context.capitalize()} escapes project root: {label}") from None
             continue
         if not create:
-            raise ValueError(f"Shared infrastructure directory does not exist: {label}")
+            raise ValueError(f"{context.capitalize()} does not exist: {label}")
         current.mkdir()
         if current.is_symlink():
-            raise SymlinkedSharedPathError(f"Refusing to use symlinked shared infrastructure directory: {label}")
+            raise SymlinkedSharedPathError(f"Refusing to use symlinked {context}: {label}")
         try:
             current.resolve().relative_to(root)
         except (OSError, ValueError):
-            raise ValueError(f"Shared infrastructure directory escapes project root: {label}") from None
+            raise ValueError(f"{context.capitalize()} escapes project root: {label}") from None
 
 
 def _validate_safe_shared_directory(project_path: Path, directory: Path) -> None: