feat(card): a folder shows every bundle under it, as the server does

`okf card <folder>` prints `okf_list` and `okf_describe` with no bundle
named, joined by `mcp_server.overview`, and computes nothing of its own:
one source, two doors. Chosen over a separate `--root` flag because the
skill's first step must be the same command whether it was pointed at a
bundle or at a folder of them; the rule that decides is discovery's own
(a directory carrying an `index.md` is a bundle). A bundle path prints its
card as before.

v1.1 order F, part F1.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/llm_ingestion_okf/mcp_server.py

@@ -512,6 +512,35 @@ def call_describe(surface: Surface, arguments: Mapping[str, Any]) -> dict[str, A
     }
 
 
+def is_bundle(path: Path) -> bool:
+    """Whether `path` IS a bundle rather than a folder that may hold some.
+
+    The rule discovery already uses to stop descending: a directory carrying
+    an `index.md`. The command line's two doors ask it to decide which shape
+    they were pointed at, so a reader never has to say which one it holds.
+    """
+    return (path / "index.md").is_file()
+
+
+def overview(surface: Surface) -> dict[str, Any]:
+    """Every bundle under the roots and each one's card, as the command line
+    prints it for a FOLDER (`okf card <folder>`).
+
+    It is `okf_list` and `okf_describe` with no bundle named, joined, and it
+    computes nothing of its own: one source, two doors. The listing carries
+    what the cards do not -- the directory each bundle sits in, and the
+    directories that look like a bundle and cannot be read as one.
+    """
+    listing = call_list(surface, {})
+    described = call_describe(surface, {})
+    return {
+        "shape": listing["shape"],
+        "bundles": listing["bundles"],
+        "unreadable": listing["unreadable"],
+        "cards": described["cards"],
+    }
+
+
 def _questions(arguments: Mapping[str, Any]) -> list[str]:
     """`question` (one string) or `questions` (a list), never both.