fix(garden): keep indentation without frontmatter, reject malformed manifest entries

Three findings on PR #676, all reproduced first.

normalized_agent_text stripped leading whitespace before deciding whether
frontmatter existed, so two frontmatter-free agents differing only by
indentation compared equal. Blank lines ahead of a frontmatter block are
formatting; ahead of anything else they are body content. Same mistake as the
body.strip() fix in the previous commit, one level up.

A plugins list holding a non-object entry was counted as valid, letting garbage
drive an error-severity stale-count finding. The count is unknown unless every
entry is an object.

check_marketplace_consistency then crashed outright on that input with
AttributeError, and on a non-object root as well. Both now report
MARKETPLACE_SHAPE and carry on. That crash predates this PR.

tools/doc_gardener.py

@@ -392,7 +392,26 @@ def check_marketplace_consistency(report: Report) -> None:
     # missing LOCAL entries as orphans — externals legitimately don't have a plugins/<name>/.
     local_entries: dict[str, dict] = {}
     external_names: set[str] = set()
-    for entry in data.get("plugins", []):
+    entries = data.get("plugins", []) if isinstance(data, dict) else None
+    if not isinstance(entries, list):
+        report.add(
+            kind="MARKETPLACE_SHAPE",
+            severity="error",
+            path=MARKETPLACE_JSON,
+            message="expected an object with a `plugins` list at the top level",
+            fix='Restore the manifest shape: {"plugins": [ ... ]}.',
+        )
+        return
+    for position, entry in enumerate(entries):
+        if not isinstance(entry, dict):
+            report.add(
+                kind="MARKETPLACE_SHAPE",
+                severity="error",
+                path=MARKETPLACE_JSON,
+                message=f"plugins[{position}] is {type(entry).__name__}, expected an object",
+                fix="Remove the entry or give it the usual name/source/description fields.",
+            )
+            continue
         name = entry.get("name")
         if not name:
             continue
@@ -437,7 +456,12 @@ def normalized_agent_text(text: str) -> str:
     a closing `---` at end of file, and a trailing space after a delimiter from
     reading as drift. A `name:` line in the body is body content and still counts.
     """
-    text = text.lstrip(BOM).lstrip()
+    text = text.lstrip(BOM)
+    trimmed = text.lstrip()
+    # Blank lines ahead of a frontmatter block are formatting. Ahead of anything else
+    # they are body content, and stripping them would hide an indentation difference.
+    if trimmed.startswith("---"):
+        text = trimmed
     fields, body = parse_frontmatter(text)
     fields.pop("name", None)
     rendered = "\n".join(f"{key}: {fields[key]!r}" for key in sorted(fields))
@@ -465,7 +489,9 @@ def actual_counts(report: Report) -> dict[str, int | None]:
         # Valid JSON of the wrong shape is still an unknown count, not a crash.
         if isinstance(manifest, dict):
             entries = manifest.get("plugins")
-            if isinstance(entries, list):
+            # A list holding a non-object entry is malformed. Counting it would let
+            # garbage drive an error-severity finding.
+            if isinstance(entries, list) and all(isinstance(e, dict) for e in entries):
                 plugins = len(entries)
     return {
         "plugins": plugins,

tools/tests/test_doc_gardener.py

@@ -9,6 +9,7 @@ import pytest
 from tools.doc_gardener import (
     CHECKS,
     Report,
+    actual_counts,
     check_agent_divergence,
     check_codex_skill_caps,
     check_dead_links,
@@ -491,6 +492,20 @@ class TestDocCounts:
         assert len(stale) == 1
         assert "30 agents" in stale[0].message
 
+    def test_malformed_plugin_entry_makes_the_count_unknown(
+        self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+    ):
+        """A plugins list holding a non-object must not drive an error-severity count."""
+        _patch_paths(monkeypatch, tmp_path)
+        _write_counts_fixture(tmp_path, plugins=12, agents=34)
+        (tmp_path / ".claude-plugin" / "marketplace.json").write_text('{"plugins": [null, null]}')
+        (tmp_path / "README.md").write_text("We ship 99 plugins today.\n")
+
+        report = Report()
+        check_doc_counts(report)
+        assert [f for f in report.findings if f.kind == "STALE_COUNT"] == []
+        assert actual_counts(Report())["plugins"] is None
+
     def test_docs_subtotals_are_not_scanned(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch):
         """Per-category subtotals under docs/ legitimately differ from the totals."""
         _patch_paths(monkeypatch, tmp_path)
@@ -679,6 +694,20 @@ class TestAgentDivergence:
         check_agent_divergence(report)
         assert report.findings == []
 
+    def test_indentation_without_frontmatter_is_content(
+        self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+    ):
+        """Leading blanks are only formatting when they sit ahead of frontmatter."""
+        _patch_paths(monkeypatch, tmp_path)
+        for plugin, body in (("alpha", "    prose here\n"), ("beta", "prose here\n")):
+            agents_dir = tmp_path / "plugins" / plugin / "agents"
+            agents_dir.mkdir(parents=True, exist_ok=True)
+            (agents_dir / "reviewer.md").write_text(body)
+
+        report = Report()
+        check_agent_divergence(report)
+        assert [f.kind for f in report.findings] == ["AGENT_BODY_DIVERGENT"]
+
     def test_groups_variants_in_message(self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch):
         """Three copies sharing two bodies report as 3 copies / 2 versions."""
         _patch_paths(monkeypatch, tmp_path)
@@ -732,3 +761,35 @@ class TestUnreadableFiles:
         unreadable = [f for f in report.findings if f.kind == "UNREADABLE_FILE"]
         assert unreadable
         assert unreadable[0].severity == "error"
+
+
+# ── Marketplace shape ────────────────────────────────────────────────────────
+
+
+class TestMarketplaceShape:
+    def test_non_object_entry_is_reported_not_raised(
+        self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+    ):
+        _patch_paths(monkeypatch, tmp_path)
+        mp = tmp_path / ".claude-plugin"
+        mp.mkdir(parents=True, exist_ok=True)
+        (mp / "marketplace.json").write_text('{"plugins": [null]}')
+        (tmp_path / "plugins").mkdir(exist_ok=True)
+
+        report = Report()
+        check_marketplace_consistency(report)  # must not raise
+        shape = [f for f in report.findings if f.kind == "MARKETPLACE_SHAPE"]
+        assert shape and "plugins[0] is NoneType" in shape[0].message
+
+    def test_non_object_root_is_reported_not_raised(
+        self, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+    ):
+        _patch_paths(monkeypatch, tmp_path)
+        mp = tmp_path / ".claude-plugin"
+        mp.mkdir(parents=True, exist_ok=True)
+        (mp / "marketplace.json").write_text("[]")
+        (tmp_path / "plugins").mkdir(exist_ok=True)
+
+        report = Report()
+        check_marketplace_consistency(report)  # must not raise
+        assert [f for f in report.findings if f.kind == "MARKETPLACE_SHAPE"]