chore: prepare v1.51.5 release (#331)

* docs: update circular ref behavior and join tool docs for v1.51.5

- parser/doc.go: clarify that non-circular refs are now resolved normally
  even when circular refs exist (changed in #329)
- docs/mcp-server.md: add missing semantic_dedup param and rename strategy
  to join tool reference table

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* chore: bump plugin version to 1.51.5

* chore: add benchmark results for v1.51.5

Generated by CI benchmark workflow on chore/v1.51.5-release-prep

🤖 Generated automatically

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: 3 people

.claude-plugin/marketplace.json

@@ -10,7 +10,7 @@
     {
       "name": "oastools",
       "description": "15 MCP tools and 5 guided skills for working with OpenAPI specs — validate, fix, convert, diff, join, overlay, generate, and walk operations/schemas/parameters/responses/security/paths",
-      "version": "1.51.4",
+      "version": "1.51.5",
       "author": {
         "name": "erraggy",
         "url": "https://github.com/erraggy"