fix(bundler): treat an explicit-null manifest field as missing, not the text "None" (#3798)

BundleManifest.from_dict read every required scalar as
`str(raw.get(key, "")).strip()`. The `""` default only covers a MISSING key. A
key present but null -- exactly how YAML spells an empty field (`author:` with
nothing after it) -- yields None, and `str(None)` is the literal string "None".
That value is non-empty, so it sailed past the `if not value` required-field
checks in structural_errors().

Reproduced on main:

    bundle.yml with description:/author:/license: left empty
    -> description='None'  author='None'  license='None'
    -> structural_errors() == []
    -> specify bundle validate: exit 0, "demo is well-formed and valid."

So an empty required field was silently accepted and the bundle shipped the
literal text "None" as its author/license/description -- which is what
`bundle info` and a catalog entry then display. A null `provides.<kind>[].id`
likewise became a component literally named "None".

Add a `_text()` helper beside the existing `_parse_str_list` (the file's
established "one coercion helper applied at every site" shape) mapping an
explicit null to "", and route the required scalars through it. Same
silent-acceptance class as the already-merged guards in this function: #3629
(non-mapping `integration:`) and #3661 (falsy non-mapping requires/provides).

Non-null values are still `str()`-coerced and stripped, and an absent key
already produced "" -- so valid manifests are byte-for-byte unaffected.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/specify_cli/bundler/models/manifest.py

@@ -96,19 +96,19 @@ class BundleManifest:
         if not isinstance(data, dict):
             raise BundlerError("Manifest must be a YAML mapping at the top level.")
 
-        schema_version = str(data.get("schema_version", "")).strip()
+        schema_version = _text(data.get("schema_version"))
 
         bundle_raw = data.get("bundle")
         if not isinstance(bundle_raw, dict):
             raise BundlerError("Manifest is missing the required 'bundle' mapping.")
         meta = BundleMeta(
-            id=str(bundle_raw.get("id", "")).strip(),
-            name=str(bundle_raw.get("name", "")).strip(),
-            version=str(bundle_raw.get("version", "")).strip(),
-            role=str(bundle_raw.get("role", "")).strip(),
-            description=str(bundle_raw.get("description", "")).strip(),
-            author=str(bundle_raw.get("author", "")).strip(),
-            license=str(bundle_raw.get("license", "")).strip(),
+            id=_text(bundle_raw.get("id")),
+            name=_text(bundle_raw.get("name")),
+            version=_text(bundle_raw.get("version")),
+            role=_text(bundle_raw.get("role")),
+            description=_text(bundle_raw.get("description")),
+            author=_text(bundle_raw.get("author")),
+            license=_text(bundle_raw.get("license")),
         )
 
         requires_raw = data.get("requires")
@@ -117,7 +117,7 @@ class BundleManifest:
         elif not isinstance(requires_raw, dict):
             raise BundlerError("'requires' must be a mapping when present.")
         requires = Requires(
-            speckit_version=str(requires_raw.get("speckit_version", "")).strip(),
+            speckit_version=_text(requires_raw.get("speckit_version")),
             tools=_parse_str_list(requires_raw.get("tools"), "requires.tools"),
             mcp=_parse_str_list(requires_raw.get("mcp"), "requires.mcp"),
         )
@@ -220,6 +220,22 @@ class BundleManifest:
         return self.integration is None
 
 
+def _text(raw: Any) -> str:
+    """Coerce a manifest scalar into stripped text, mapping an explicit null to ``""``.
+
+    A ``.get(key, "")`` default only covers a *missing* key. A key that is
+    present but null -- how YAML spells an empty field (``author:`` with nothing
+    after it) -- yields ``None``, and ``str(None)`` is the literal ``"None"``.
+    That text is non-empty, so it sailed past the ``if not value`` required-field
+    checks in :meth:`BundleManifest.structural_errors`: an empty required field
+    was silently accepted and the bundle shipped ``"None"`` as its
+    author/license/description.
+    """
+    if raw is None:
+        return ""
+    return str(raw).strip()
+
+
 def _parse_str_list(raw: Any, field_name: str) -> tuple[str, ...]:
     """Coerce a manifest list-of-strings field into a tuple of strings.
 
@@ -247,7 +263,7 @@ def _parse_refs(kind: str, raw: Any) -> list[ComponentRef]:
         refs.append(
             ComponentRef(
                 kind=kind,
-                id=str(item.get("id", "")).strip(),
+                id=_text(item.get("id")),
                 version=(str(item["version"]).strip() if item.get("version") else None),
                 source=(str(item["source"]).strip() if item.get("source") else None),
                 priority=priority,