feat: add conformance scenario for SEP-2164 resource-not-found error code (#200)

* feat: add conformance scenario for SEP-2164 resource-not-found error code

Adds a draft-scoped scenario verifying servers return -32602 (Invalid
Params) for non-existent resources instead of the legacy -32002 or an
empty contents array. Includes a sep-2164.yaml traceability file mapping
each MUST/MUST NOT/SHOULD to its check per the proposed SEP-2484 process.

* fix: align SEP-2164 check severities with spec text (#246)

Splits sep-2164-error-code into:
- sep-2164-no-empty-contents (MUST NOT -> FAILURE)
- sep-2164-error-code (SHOULD -> WARNING)

Updates sep-2164.yaml to quote the spec text verbatim and adds an
excluded row for the client-side -32002 backcompat SHOULD.

See #245 for the SHOULD/WARNING tier-scoring policy discussion.

---------

Co-authored-by: Paul Carleton <paulcarletonjr@gmail.com>

src/scenarios/index.ts

@@ -45,7 +45,8 @@ import {
   ResourcesReadBinaryScenario,
   ResourcesTemplateReadScenario,
   ResourcesSubscribeScenario,
-  ResourcesUnsubscribeScenario
+  ResourcesUnsubscribeScenario,
+  ResourcesNotFoundErrorScenario
 } from './server/resources';
 
 import {
@@ -123,6 +124,9 @@ const allClientScenariosList: ClientScenario[] = [
   new ResourcesSubscribeScenario(),
   new ResourcesUnsubscribeScenario(),
 
+  // Resources error handling (SEP-2164)
+  new ResourcesNotFoundErrorScenario(),
+
   // Prompts scenarios
   new PromptsListScenario(),
   new PromptsGetSimpleScenario(),