feat(certificates): orphan-cert attachment gate + render early-return

Block fp.certificate.action_issue on Nadcap / Mill Test / Customer-
Specific certs when attachment_id is empty. These three cert types
are manual-attach only — operator uploads the supplier doc /
regulator-issued cert / filled customer template PDF before the
cert can be issued. Prevents shipping the customer an empty PDF.

_fp_render_and_attach_pdf gets an early-return guard so an orphan-
type cert never tries to render a CoC QWeb template.

Sub: docs/superpowers/specs/2026-05-27-recipe-cert-toggles-design.md
Task: T5. Makes test_orphan_cert_issue_blocks_without_attachment pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

fusion_plating/fusion_plating_certificates/models/fp_certificate.py

@@ -551,6 +551,27 @@ class FpCertificate(models.Model):
                     'name': rec.name or rec.display_name,
                     'c':    rec.contact_partner_id.name,
                 })
+            # Orphan cert types (Nadcap / Mill Test / Customer-Specific)
+            # are manual-attach only — operator uploads supplier doc /
+            # regulator-issued cert / filled customer template. Block
+            # issuance until an attachment is present so the customer
+            # doesn't receive an empty PDF. See spec 2026-05-27.
+            ORPHAN_TYPES = ('nadcap_cert', 'mill_test', 'customer_specific')
+            if (rec.certificate_type in ORPHAN_TYPES
+                    and not rec.attachment_id):
+                type_label = dict(
+                    rec._fields['certificate_type'].selection
+                ).get(rec.certificate_type, rec.certificate_type)
+                raise UserError(_(
+                    'Cannot issue %(type)s "%(name)s" — no PDF attached.'
+                    '\n\nThis certificate type expects a PDF you upload '
+                    'from disk (supplier doc / regulator-issued cert / '
+                    'filled customer template). Upload the PDF to the '
+                    'Attachment field on this cert before clicking Issue.'
+                ) % {
+                    'type': type_label,
+                    'name': rec.name or rec.display_name,
+                })
             # Thickness data requirement — unified gate covering both
             # cert types. A customer needs thickness data on the cert
             # when ANY of these is true:
@@ -729,6 +750,13 @@ class FpCertificate(models.Model):
         import base64
         import io
         self.ensure_one()
+        # Orphan cert types (Nadcap / Mill Test / Customer-Specific) are
+        # manual-attach only — never render a CoC QWeb template for them.
+        # action_issue's precondition gate already enforces the
+        # attachment requirement, so by the time we get here the operator
+        # has uploaded the right PDF. See spec 2026-05-27 §4.
+        if self.certificate_type != 'coc':
+            return self.attachment_id or False
         if self.attachment_id:
             return self.attachment_id
         report = (