fix(tests): apply user edits when creating test from template

The form captured name/description/platform/procedure/tool edits but
never sent them — the created test always used the raw template values.

- TestTemplateInstantiate schema: add optional override fields
  (name, description, platform, procedure_text, tool_used)
- create_test_from_template service: accept *_override kwargs;
  use override value when provided, fall back to template value
- Router: pass all override fields from payload to service
- Frontend API createTestFromTemplate: accept overrides object, spread into body
- TestFromTemplateForm: pass all form state values as overrides

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/services/test_crud_service.py

@@ -93,10 +93,17 @@ def create_test_from_template(
     template_id: uuid.UUID,
     technique_id_or_mitre: str,
     creator_id: uuid.UUID,
+    # Optional user-edited overrides (take priority over template values)
+    name_override: str | None = None,
+    description_override: str | None = None,
+    platform_override: str | None = None,
+    procedure_text_override: str | None = None,
+    tool_used_override: str | None = None,
 ) -> Test:
     """Instantiate a Test from a TestTemplate.
 
     technique_id_or_mitre can be a UUID string or MITRE ID (e.g. T1059.001).
+    Override fields, when provided, take precedence over the template's values.
     Raises EntityNotFoundError if template or technique not found.
     Does not commit; caller uses UnitOfWork.
     """
@@ -121,11 +128,11 @@ def create_test_from_template(
 
     test = Test(
         technique_id=technique.id,
-        name=template.name,
-        description=template.description,
-        platform=template.platform,
-        procedure_text=template.attack_procedure,
-        tool_used=template.tool_suggested,
+        name=name_override if name_override is not None else template.name,
+        description=description_override if description_override is not None else template.description,
+        platform=platform_override if platform_override is not None else template.platform,
+        procedure_text=procedure_text_override if procedure_text_override is not None else template.attack_procedure,
+        tool_used=tool_used_override if tool_used_override is not None else template.tool_suggested,
         remediation_steps=template.suggested_remediation,
         created_by=creator_id,
         state=TestState.draft,