docs: Cerebral Valley Opus 4.7 hackathon submission packet

- AIReasoner default model now claude-opus-4-7 (was sonnet-4-6); pipeline
  reads ai.model from config and passes to constructor. The reasoner
  class attribute is also Opus 4.7 so any caller without explicit model
  defaults to the hackathon model
- README hero gains a "Built with Claude Opus 4.7" badge + a line linking
  to the Cerebral Valley × Anthropic hackathon page
- New SUBMISSION.md — copy-paste blocks for every field of the
  submission form: name, taglines, short / long description, "how Claude
  is used" detail, GitHub URL, demo instructions, tags, tech stack,
  team, license, and a final pre-submission checklist

analysis/ai_reasoner.py

@@ -73,11 +73,13 @@ class AIReasoner:
     Falls back gracefully if API key is missing or call fails.
     """
 
-    MODEL   = "claude-sonnet-4-6"
+    MODEL   = "claude-opus-4-7"   # default — overridden by config.ai.model when present
     API_URL = "https://api.anthropic.com/v1/messages"
     TIMEOUT = 30  # seconds
 
-    def __init__(self, api_key: Optional[str] = None):
+    def __init__(self, api_key: Optional[str] = None, model: Optional[str] = None):
+        if model:
+            self.MODEL = model
         # If the caller passes a placeholder like "${ANTHROPIC_API_KEY}" or an
         # empty string, treat it as missing and fall back to the env var.
         candidate = (api_key or "").strip()