Keep typescript on 5.9.x until openapi-typescript supports TS 6

The Dependabot group update bumped typescript to ^6.0.2, but
openapi-typescript@7.13.0 still declares peer typescript ^5.x, so
npm ci fails to resolve. Revert just the typescript bump (keep the
other five: @types/node, @vitest/coverage-v8, msw, oxlint, vitest)
and regenerate the lockfile against 5.9.3.

Add a temporary dependabot.yml ignore on typescript semver-major
bumps so the same mismatch doesn't keep getting proposed. Remove
the ignore once openapi-typescript ships TS 6 support
(openapi-ts/openapi-typescript#2774).

Author: jeremy

.github/dependabot.yml

@@ -19,6 +19,11 @@ updates:
         patterns: ["*"]
     cooldown:
       default-days: 10
+    ignore:
+      # TEMPORARY: openapi-typescript peer dep still pins typescript ^5.x.
+      # Remove once openapi-typescript ships TS 6 support (tracking openapi-ts/openapi-typescript#2774).
+      - dependency-name: typescript
+        update-types: ["version-update:semver-major"]
 
   - package-ecosystem: bundler
     directory: /ruby