feat(scenarios,environments): add markdown description field

- add optional description to scenario and environment entities
- expose description in create/update DTOs, MCP tools, and export DTOs
- render description as markdown on detail pages
- add description editor (CodeEditor) to create/edit forms for both resources

client/src/api/client.ts

@@ -133,13 +133,13 @@ export const environments = {
   get(id: string): Promise<Environment> {
     return request(`/environments/${id}`);
   },
-  create(name: string, data: Environment['data']): Promise<Environment> {
+  create(name: string, data: Environment['data'], description?: string): Promise<Environment> {
     return request('/environments', {
       method: 'POST',
-      body: JSON.stringify({ name, data }),
+      body: JSON.stringify({ name, description, data }),
     });
   },
-  update(id: string, patch: Partial<Pick<Environment, 'name' | 'data'>>): Promise<Environment> {
+  update(id: string, patch: Partial<Pick<Environment, 'name' | 'description' | 'data'>>): Promise<Environment> {
     return request(`/environments/${id}`, {
       method: 'PATCH',
       body: JSON.stringify(patch),
@@ -182,13 +182,13 @@ export const scenarios = {
   get(id: string): Promise<Scenario & { steps: ScenarioStep[] }> {
     return request(`/scenarios/${id}`);
   },
-  create(name: string): Promise<Scenario> {
+  create(name: string, description?: string): Promise<Scenario> {
     return request('/scenarios', {
       method: 'POST',
-      body: JSON.stringify({ name }),
+      body: JSON.stringify({ name, description }),
     });
   },
-  update(id: string, patch: Partial<Pick<Scenario, 'name'>>): Promise<Scenario> {
+  update(id: string, patch: Partial<Pick<Scenario, 'name' | 'description'>>): Promise<Scenario> {
     return request(`/scenarios/${id}`, {
       method: 'PATCH',
       body: JSON.stringify(patch),