fix(express): show Tax on totals + add tooling as real SO line

Three related fixes on the Express Orders totals card:

1. Totals card now breaks out Subtotal / Tax / Tooling Charge /
   Grand Total. Previously the "Subtotal" and "Grand Total" rows
   both read from total_amount (same value rendered twice) and no
   tax was shown at all. Customers on a fiscal position-mapped
   tax rate (Ontario HST, etc.) had their taxes silently dropped
   from the preview.

2. tooling_charge now feeds the Grand Total. The total_amount
   compute previously summed line subtotals only. Added a real
   SO line for the tooling charge in action_create_order so the
   eventual sale.order.amount_total matches the preview AND the
   invoice carries a "Tooling Charge" line item.

3. tax_ids is now visible as an optional column on the lines
   list. Operator can see + override the auto-applied tax per
   line. Default still comes from FP-SERVICE product mapped
   through partner.property_account_position_id (fiscal position).

New compute fields on fp.direct.order.wizard:
  - total_subtotal (sum of line.qty * line.unit_price, pre-tax)
  - total_tax (sum of line + tooling taxes via compute_all)
  - total_amount (subtotal + tax + tooling — was just subtotal)

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

fusion_plating/fusion_plating_configurator/wizard/fp_direct_order_wizard.py

@@ -342,9 +342,24 @@ class FpDirectOrderWizard(models.Model):
     line_ids = fields.One2many(
         'fp.direct.order.line', 'wizard_id', string='Order Lines',
     )
-    total_amount = fields.Monetary(
-        string='Order Total',
+    total_subtotal = fields.Monetary(
+        string='Subtotal (pre-tax)',
         compute='_compute_totals', currency_field='currency_id',
+        help='Sum of (qty × unit_price) across all lines, before tax. '
+             'Excludes the tooling charge.',
+    )
+    total_tax = fields.Monetary(
+        string='Tax',
+        compute='_compute_totals', currency_field='currency_id',
+        help='Sum of taxes across all lines + the tooling charge. '
+             'Each line uses the partner\'s fiscal position to map the '
+             'FP-SERVICE product taxes to the right rate.',
+    )
+    total_amount = fields.Monetary(
+        string='Grand Total',
+        compute='_compute_totals', currency_field='currency_id',
+        help='Subtotal + tax + tooling charge. Matches the eventual '
+             'sale.order.amount_total when the order is confirmed.',
     )
     total_qty = fields.Integer(string='Total Qty', compute='_compute_totals')
     total_line_count = fields.Integer(
@@ -366,10 +381,66 @@ class FpDirectOrderWizard(models.Model):
         return super().create(vals_list)
 
     # ---- Computes ----
-    @api.depends('line_ids.line_subtotal', 'line_ids.quantity')
+    @api.depends(
+        'line_ids.line_subtotal',
+        'line_ids.quantity',
+        'line_ids.unit_price',
+        'line_ids.tax_ids',
+        'tooling_charge',
+        'partner_id',
+        'currency_id',
+    )
     def _compute_totals(self):
+        """Roll up subtotal / tax / grand total across lines + tooling.
+
+        Each line's taxes are computed via account.tax.compute_all so the
+        Express form's totals card mirrors what the eventual SO will show
+        once the operator hits Confirm. The tooling charge is added at the
+        wizard level here AND pushed as an actual sale.order.line at
+        action_create_order time (so it carries into the invoice).
+        """
         for rec in self:
-            rec.total_amount = sum(rec.line_ids.mapped('line_subtotal'))
+            subtotal = 0.0
+            tax_total = 0.0
+            for line in rec.line_ids:
+                line_pre_tax = (line.quantity or 0) * (line.unit_price or 0.0)
+                subtotal += line_pre_tax
+                if line.tax_ids and line_pre_tax:
+                    taxes_res = line.tax_ids.compute_all(
+                        line.unit_price or 0.0,
+                        currency=rec.currency_id,
+                        quantity=line.quantity or 0,
+                        product=None,
+                        partner=rec.partner_id or None,
+                    )
+                    tax_total += (
+                        taxes_res['total_included']
+                        - taxes_res['total_excluded']
+                    )
+            # Tooling charge: pick the tax set from the FIRST line that
+            # has one (best proxy for the customer's standard rate). If
+            # no line has taxes set yet, tooling is shown untaxed in the
+            # preview; the eventual SO line will apply product defaults.
+            tooling = rec.tooling_charge or 0.0
+            if tooling:
+                first_taxed_line = next(
+                    (l for l in rec.line_ids if l.tax_ids), False,
+                )
+                if first_taxed_line:
+                    tooling_res = first_taxed_line.tax_ids.compute_all(
+                        tooling,
+                        currency=rec.currency_id,
+                        quantity=1,
+                        product=None,
+                        partner=rec.partner_id or None,
+                    )
+                    tax_total += (
+                        tooling_res['total_included']
+                        - tooling_res['total_excluded']
+                    )
+            rec.total_subtotal = subtotal
+            rec.total_tax = tax_total
+            rec.total_amount = subtotal + tax_total + tooling
             rec.total_qty = sum(rec.line_ids.mapped('quantity'))
             rec.total_line_count = len(rec.line_ids)
 
@@ -824,6 +895,30 @@ class FpDirectOrderWizard(models.Model):
                             if line.tax_ids else False),
             }))
 
+        # 4b. Tooling charge — surface as a real sale.order.line so it
+        # carries through SO.amount_total + invoice naturally, instead of
+        # sitting orphaned on the SO header. Tax: inherit from the first
+        # part line that has taxes set (best proxy for "the customer's
+        # standard tax rate"); falls back to product defaults if no line
+        # has taxes yet.
+        if self.tooling_charge:
+            tooling_taxes = False
+            first_taxed = next(
+                (l for l in self.line_ids if l.tax_ids), False,
+            )
+            if first_taxed:
+                tooling_taxes = [(6, 0, first_taxed.tax_ids.ids)]
+            so_vals['order_line'].append((0, 0, {
+                'product_id': product.id,
+                'name': _('Tooling Charge'),
+                'product_uom_qty': 1.0,
+                'price_unit': self.tooling_charge,
+                'x_fc_internal_description': _(
+                    'One-time tooling fee added via Express Orders.'
+                ),
+                'tax_ids': tooling_taxes,
+            }))
+
         # 5. Create — stays in draft / quotation. Sub 1: user reviews
         # and manually clicks Confirm / Send. No auto-confirm, no
         # auto-email to the client.