fix(bundler): reject non-mapping 'integration' in a bundle manifest (#3629)

BundleManifest.from_dict guarded 'requires' and 'provides' with
"must be a mapping when present", but a present-but-non-mapping 'integration'
(e.g. a bare string "copilot") silently failed the isinstance(dict) check and
was dropped — leaving the bundle wrongly integration-agnostic (is_agnostic()
True) instead of surfacing the authoring mistake. Add the same guard so
'integration' is consistent with its sibling mapping fields.

Test: integration='copilot' now raises BundlerError (fails before: silently
dropped, no raise).

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/specify_cli/bundler/models/manifest.py

@@ -122,6 +122,11 @@ class BundleManifest:
 
         integration = None
         integration_raw = data.get("integration")
+        # Mirror the requires/provides guards above: a present-but-non-mapping
+        # 'integration' (e.g. a bare string "copilot") was silently dropped,
+        # leaving the bundle wrongly integration-agnostic. Reject it instead.
+        if integration_raw is not None and not isinstance(integration_raw, dict):
+            raise BundlerError("'integration' must be a mapping when present.")
         if isinstance(integration_raw, dict) and integration_raw.get("id"):
             integration = IntegrationRef(id=str(integration_raw["id"]).strip())