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>

frontend/src/api/tests.ts

@@ -91,14 +91,22 @@ export async function createTest(payload: TestCreatePayload): Promise<Test> {
   return data;
 }
 
-/** Create a test from an existing template. */
+/** Create a test from an existing template, with optional field overrides. */
 export async function createTestFromTemplate(
   templateId: string,
   techniqueId: string,
+  overrides?: {
+    name?: string;
+    description?: string;
+    platform?: string;
+    procedure_text?: string;
+    tool_used?: string;
+  },
 ): Promise<Test> {
   const { data } = await client.post<Test>("/tests/from-template", {
     template_id: templateId,
     technique_id: techniqueId,
+    ...overrides,
   });
   return data;
 }