feat: add dialectic_submit_verdict tool (was missing — judge had no way to submit)

7 tools total now:
- dialectic_list_topics
- dialectic_topic_detail
- dialectic_propose_topic
- dialectic_signup
- dialectic_post_argument
- dialectic_submit_verdict (NEW — POST /api/topics/{id}/verdict)
- dialectic_view_verdict

Also added contracts.tools entry for the new tool, updated README +
startup log line. Sim smoke verified the other 4 (list/propose/signup/
detail) via direct plugin import; submit_verdict not yet smoke-tested
end-to-end (requires running through a full debate to debate_end_at).
Code path is identical to other write tools — bearer + JSON body +
shape-coerced response.

plugin/index.ts

@@ -3,7 +3,8 @@
  *
  * Tools: dialectic_list_topics, dialectic_topic_detail,
  *        dialectic_propose_topic, dialectic_signup,
- *        dialectic_post_argument, dialectic_view_verdict
+ *        dialectic_post_argument, dialectic_submit_verdict,
+ *        dialectic_view_verdict
  *
  * Loader gotchas (per [[reference-meridian-plugin-contract]]):
  *   - openclaw.plugin.json MUST declare `activation.onStartup: true`