fix(tests+ci): update 42→43 skill count, fix E2E artifact path

- Unit/integration tests: update hardcoded 42→43 in 7 test files
  (agentSkillTools-mcp, agentSkills-catalog, agentSkills-generator,
  agent-skills-content, agent-skills-discovery, listCapabilities-a2a)
  to match the 43rd skill (config-codex-cli) added in the previous commit.
- Include CONFIG_SKILL_IDS in integration content test ALL_IDS so
  skills/config-codex-cli/ is no longer "unexpected".
- listCapabilities.ts: change totalSkills from literal 42 to catalog.length
  so it adapts to catalog growth automatically.
- computeCoverage assertions: include config.have in totalSkills check.
- CI: switch E2E artifact from upload-artifact path (ambiguous stripping)
  to explicit tar archive. Fixes "Could not find a production build in
  ./.build/next" — the previous approach's download path was double-nested
  (.build/next/next/...) due to upload-artifact LCA computation. tar -czf
  stores .build/next/... relative to CWD; tar -xzf restores them verbatim.
- Also exclude .build/next/cache from the tar to keep archive lean.
- feat(translator): strip client_metadata in Responses→Chat translation
  (Mistral 422 extra_forbidden fix); add regression test.

.github/workflows/ci.yml

@@ -144,15 +144,20 @@ jobs:
       - run: npm ci
       - run: npm run check:node-runtime
       - run: npm run build
+      - name: Archive Next.js build for E2E shards
+        # Use tar so the archive preserves paths relative to CWD (.build/next/...).
+        # upload-artifact path-stripping is ambiguous when exclude patterns are used;
+        # an explicit tar avoids the double-nesting issue (.build/next/next/...).
+        run: |
+          tar -czf /tmp/e2e-build.tar.gz \
+            --exclude='.build/next/standalone/node_modules' \
+            --exclude='.build/next/cache' \
+            .build/next
       - name: Upload Next.js build for E2E shards
         uses: actions/upload-artifact@v4
         with:
           name: e2e-next-build
-          # Exclude standalone/node_modules (558MB) — each shard already runs
-          # npm ci, so we cp node_modules into standalone after the download.
-          path: |
-            .build/next/
-            !.build/next/standalone/node_modules/
+          path: /tmp/e2e-build.tar.gz
           retention-days: 1
 
   package-artifact:
@@ -544,9 +549,11 @@ jobs:
         uses: actions/download-artifact@v4
         with:
           name: e2e-next-build
-          path: .build/next/
-      - name: Restore standalone node_modules from npm ci
-        run: cp -r node_modules .build/next/standalone/node_modules
+          path: /tmp/
+      - name: Extract Next.js build and restore standalone node_modules
+        run: |
+          tar -xzf /tmp/e2e-build.tar.gz
+          cp -r node_modules .build/next/standalone/node_modules
       - run: npx playwright test tests/e2e/*.spec.ts --shard=${{ matrix.shard }}/9
 
   test-integration: