sync(docs[SyncResult,update_repo]): Add NumPy-style docstrings

why: Code review identified incomplete docstrings missing Parameters
and Returns sections required by project standards.
what:
- Add Parameters/Returns to SyncResult.__bool__() and add_error()
- Add Parameters/Returns to GitSync.update_repo()
- Add Returns to HgSync.update_repo()
- Add Parameters/Returns to SvnSync.update_repo()

Author: tony

src/libvcs/sync/base.py

@@ -61,7 +61,13 @@ class SyncResult:
     errors: list[SyncError] = dataclasses.field(default_factory=list)
 
     def __bool__(self) -> bool:
-        """Return True if the sync succeeded without errors."""
+        """Return True if the sync succeeded without errors.
+
+        Returns
+        -------
+        bool
+            True if no errors were recorded, False otherwise.
+        """
         return self.ok
 
     def add_error(
@@ -70,7 +76,17 @@ def add_error(
         message: str,
         exception: Exception | None = None,
     ) -> None:
-        """Record an error and mark the result as failed."""
+        """Record an error and mark the result as failed.
+
+        Parameters
+        ----------
+        step : str
+            Name of the sync step that failed (e.g. ``"fetch"``, ``"checkout"``).
+        message : str
+            Human-readable description of the error.
+        exception : Exception or None, optional
+            The underlying exception, if available.
+        """
         self.ok = False
         self.errors.append(SyncError(step=step, message=message, exception=exception))
 

src/libvcs/sync/git.py

@@ -382,7 +382,18 @@ def update_repo(
         *args: t.Any,
         **kwargs: t.Any,
     ) -> SyncResult:
-        """Pull latest changes from git remote."""
+        """Pull latest changes from git remote.
+
+        Parameters
+        ----------
+        set_remotes : bool
+            If True, configure remotes before updating.
+
+        Returns
+        -------
+        SyncResult
+            Result of the sync operation, with any errors recorded.
+        """
         result = SyncResult()
         self.ensure_dir()
 

src/libvcs/sync/hg.py

@@ -66,7 +66,13 @@ def get_revision(self) -> str:
         return self.run(["parents", "--template={rev}"])
 
     def update_repo(self, *args: t.Any, **kwargs: t.Any) -> SyncResult:
-        """Pull changes from remote Mercurial repository into this one."""
+        """Pull changes from remote Mercurial repository into this one.
+
+        Returns
+        -------
+        SyncResult
+            Result of the sync operation, with any errors recorded.
+        """
         result = SyncResult()
         if not pathlib.Path(self.path / ".hg").exists():
             self.obtain()

src/libvcs/sync/svn.py

@@ -150,7 +150,18 @@ def update_repo(
         *args: t.Any,
         **kwargs: t.Any,
     ) -> SyncResult:
-        """Fetch changes from SVN repository to local working copy."""
+        """Fetch changes from SVN repository to local working copy.
+
+        Parameters
+        ----------
+        dest : str or None, optional
+            Destination path override for the working copy.
+
+        Returns
+        -------
+        SyncResult
+            Result of the sync operation, with any errors recorded.
+        """
         result = SyncResult()
         self.ensure_dir()
         if pathlib.Path(self.path / ".svn").exists():