cli(add[help]) Cover every add permutation

why: the examples showed three path-mode invocations, leaving the URL
argument, --name, --pin, --shallow, --depth, --file, --yes and
--no-merge with no worked example in `vcspull add --help` or in the
generated docs, which render from this same block.

what:
- Show both positional modes, the --name fallback for a URL with no
  nameable segment, and the recorded-remote form
- Group revision and clone-depth examples under "Pinning" and
  unattended invocations under "Automation", following the grouped
  shape tmuxp's search help uses

Author: tony

src/vcspull/cli/__init__.py

@@ -203,11 +203,28 @@ def build_description(
             None,
             [
                 "vcspull add ~/code/mylib",
+                "vcspull add https://github.com/example/mylib.git",
                 "vcspull add ~/src/mylib --workspace ~/code",
-                (
-                    "vcspull add ~/code/mylib "
-                    "--url https://github.com/example/mylib.git --dry-run"
-                ),
+                "vcspull add https://git.example.com/.git --name mylib",
+                ("vcspull add ~/code/mylib --url https://github.com/example/mylib.git"),
+            ],
+        ),
+        (
+            "Pinning",
+            [
+                "vcspull add ~/code/mylib --pin v1.0",
+                "vcspull add git+https://github.com/example/mylib.git@v1.0",
+                "vcspull add ~/code/mylib --shallow",
+                "vcspull add ~/code/mylib --depth 50",
+            ],
+        ),
+        (
+            "Automation",
+            [
+                "vcspull add ~/code/mylib --dry-run",
+                "vcspull add https://github.com/example/mylib.git --yes",
+                "vcspull add ~/code/mylib --file ~/configs/python.yaml",
+                "vcspull add ~/code/mylib --no-merge",
             ],
         ),
     ),