fix(sep-2243): collapse check IDs to one-per-requirement (#287)

The sep-2243 scenario check IDs drifted from the requirement-traceability
yaml in #259 — the code emitted one ID per test case while the yaml
declares one per normative requirement, so the IDs no longer matched.

Rename the emitted IDs so a check ID maps to a single MUST/SHOULD and is
emitted once per case (the per-case detail moves to name/description),
matching the repo's existing 'same id, vary status/message' convention:

- mcp-method-header-* / mcp-name-header-*  -> client-includes-standard-headers
- reject-invalid-tool-* / keep-valid-tool  -> client-reject-invalid-tool
- server-accepts-{lower,upper}case-name    -> header-name-case-insensitive
- server reject status checks (mismatch/missing/case x method/name)
                                            -> server-reject-invalid-headers
- their error-code variants                 -> server-reject-error-code

Merge the yaml's server-reject-mismatch + server-reject-status into one
server-reject-invalid-headers MUST (HTTP 400 on a header-validation
failure); keep server-reject-error-code as the SHOULD. Base64/custom-header
rejection checks keep their own param-validation IDs (out of scope here).

Gates and the whitespace-acceptance check keep their scenario-matching
names. No behavior change — only check IDs, descriptions, and the yaml.

src/scenarios/client/http-custom-headers.ts

@@ -626,7 +626,7 @@ export class HttpInvalidToolHeadersScenario extends BaseHttpScenario {
     // Check that valid_tool WAS called — proves client kept valid tools
     const validToolCalled = this.calledTools.has('valid_tool');
     this.checks.push({
-      id: 'sep-2243-keep-valid-tool',
+      id: 'sep-2243-client-reject-invalid-tool',
       name: 'ClientKeepsValidTool',
       description: 'Client MUST keep valid tools while excluding invalid ones',
       status: validToolCalled ? 'SUCCESS' : 'FAILURE',
@@ -654,7 +654,7 @@ export class HttpInvalidToolHeadersScenario extends BaseHttpScenario {
     for (const toolName of invalidTools) {
       const called = this.calledTools.has(toolName);
       this.checks.push({
-        id: `sep-2243-reject-invalid-tool-${toolName.replace(/_/g, '-')}`,
+        id: 'sep-2243-client-reject-invalid-tool',
         name: `ClientRejectsInvalidTool_${toolName}`,
         description: `Client MUST NOT call tool '${toolName}' with invalid x-mcp-header`,
         status: called ? 'FAILURE' : 'SUCCESS',

src/scenarios/client/http-standard-headers.test.ts

@@ -31,14 +31,19 @@ describe('HttpStandardHeadersScenario (SEP-2243) — negative', () => {
     });
   }
 
-  it('FAILs sep-2243-mcp-method-header-initialize when Mcp-Method is missing', async () => {
+  // The coarse check id is emitted once per method/name case, so we narrow to
+  // the initialize Mcp-Method emission via its (case-specific) name.
+  const COARSE_ID = 'sep-2243-client-includes-standard-headers';
+  const INIT_METHOD_NAME = 'ClientMcpMethodHeader_initialize';
+
+  it('FAILs the initialize Mcp-Method emission when Mcp-Method is missing', async () => {
     const scenario = new HttpStandardHeadersScenario();
     const { serverUrl } = await scenario.start();
     try {
       await postInitialize(serverUrl, {}); // no Mcp-Method header
       const checks = scenario.getChecks();
       const check = checks.find(
-        (c) => c.id === 'sep-2243-mcp-method-header-initialize'
+        (c) => c.id === COARSE_ID && c.name === INIT_METHOD_NAME
       );
       expect(check?.status).toBe('FAILURE');
     } finally {
@@ -46,14 +51,14 @@ describe('HttpStandardHeadersScenario (SEP-2243) — negative', () => {
     }
   });
 
-  it('SUCCEEDs sep-2243-mcp-method-header-initialize when Mcp-Method matches', async () => {
+  it('SUCCEEDs the initialize Mcp-Method emission when Mcp-Method matches', async () => {
     const scenario = new HttpStandardHeadersScenario();
     const { serverUrl } = await scenario.start();
     try {
       await postInitialize(serverUrl, { 'Mcp-Method': 'initialize' });
       const checks = scenario.getChecks();
       const check = checks.find(
-        (c) => c.id === 'sep-2243-mcp-method-header-initialize'
+        (c) => c.id === COARSE_ID && c.name === INIT_METHOD_NAME
       );
       expect(check?.status).toBe('SUCCESS');
     } finally {

src/scenarios/client/http-standard-headers.ts

@@ -53,7 +53,7 @@ export class HttpStandardHeadersScenario extends BaseHttpScenario {
     for (const method of expectedMethods) {
       if (!this.methodHeaderChecks.has(method)) {
         result.push({
-          id: `sep-2243-mcp-method-header-${method.replace(/\//g, '-')}`,
+          id: 'sep-2243-client-includes-standard-headers',
           name: `ClientMcpMethodHeader_${method.replace(/\//g, '_')}`,
           description: `Client sends correct Mcp-Method header on ${method} request`,
           status: 'SKIPPED',
@@ -68,7 +68,7 @@ export class HttpStandardHeadersScenario extends BaseHttpScenario {
     for (const method of expectedNameMethods) {
       if (!this.nameHeaderChecks.has(method)) {
         result.push({
-          id: `sep-2243-mcp-name-header-${method.replace(/\//g, '-')}`,
+          id: 'sep-2243-client-includes-standard-headers',
           name: `ClientMcpNameHeader_${method.replace(/\//g, '_')}`,
           description: `Client sends correct Mcp-Name header on ${method} request`,
           status: 'SKIPPED',
@@ -141,7 +141,7 @@ export class HttpStandardHeadersScenario extends BaseHttpScenario {
     this.methodHeaderChecks.set(method, errors.length === 0);
 
     this.checks.push({
-      id: `sep-2243-mcp-method-header-${method.replace(/\//g, '-')}`,
+      id: 'sep-2243-client-includes-standard-headers',
       name: `ClientMcpMethodHeader_${method.replace(/\//g, '_')}`,
       description: `Client sends correct Mcp-Method header on ${method} request`,
       status: errors.length === 0 ? 'SUCCESS' : 'FAILURE',
@@ -186,7 +186,7 @@ export class HttpStandardHeadersScenario extends BaseHttpScenario {
     this.nameHeaderChecks.set(method, errors.length === 0);
 
     this.checks.push({
-      id: `sep-2243-mcp-name-header-${method.replace(/\//g, '-')}`,
+      id: 'sep-2243-client-includes-standard-headers',
       name: `ClientMcpNameHeader_${method.replace(/\//g, '_')}`,
       description: `Client sends correct Mcp-Name header on ${method} request`,
       status: errors.length === 0 ? 'SUCCESS' : 'FAILURE',