fix(configurator): Part cell row 1 shows part# / rev separately via CSS overlay

Root cause: my @api.depends_context('fp_express_part_picker') decorator
on _compute_display_name was not honored by Odoo. Verified via odoo
shell — display_name returns the full 'PART (Rev X) — Name' regardless
of context. Reason: display_name is defined on the base Model class
and Odoo registers the field metadata (incl. _depends_context) when
the field is FIRST declared. Subclass redefinitions of the compute
method don't update _depends_context after the fact.

Workaround: don't rely on display_name context override. Instead,
overlay a custom span on top of the Many2OneField that shows JUST
the part_number_display value. CSS overlay uses:
- position: absolute / inset: 0
- background: $xpr-card (matches list row background)
- z-index: 2 over the picker
- pointer-events: none so clicks pass through to the picker

When the picker is focused (:focus-within parent), the overlay
hides so the user sees the autocomplete input value as they type.
When not focused, the overlay covers display_name with just the
part number.

Row 1 now reads 'ENG-1042  /  B' — picker on the left (showing only
part_number_display), separator, revision on the right. Matches the
mockup pixel layout the user requested.

fusion_plating/fusion_plating_configurator/static/src/xml/express_part_cell.xml

@@ -11,9 +11,20 @@
 -->
 <t t-name="fusion_plating_configurator.FpExpressPartCell">
     <div class="o_fp_xpr_part_cell">
-        <!-- Row 1 — Part picker -->
+        <!-- Row 1 — Part picker (left, with part-number overlay) + / + Revision (right)
+             The overlay shows JUST the part_number_display when not focused;
+             on focus, the overlay hides so the user sees the autocomplete input. -->
         <div class="o_fp_xpr_part_row o_fp_xpr_part_id">
-            <Many2OneField t-props="props"/>
+            <div class="o_fp_xpr_part_picker_wrap">
+                <Many2OneField t-props="props"/>
+                <span t-if="hasPart"
+                      class="o_fp_xpr_part_num_overlay"
+                      t-esc="partNumber"/>
+            </div>
+            <span class="o_fp_xpr_part_sep">/</span>
+            <span class="o_fp_xpr_part_rev"
+                  t-att-class="{ 'o_fp_xpr_part_rev_empty': !partRev }"
+                  t-esc="partRev or 'rev'"/>
         </div>
         <!-- Row 2 — Editable part description (saves to part.name) -->
         <div class="o_fp_xpr_part_row o_fp_xpr_part_name">