feat(miner): Add exponential backoff and request limiting for CORE API

- MAX_REQUESTS = 1000 limit with backoff scaling (1-10s)
- Rate limiting tracks _request_count and _last_request_time
- Prevent 403 errors from exceeding API quota

Build: 2987 jobs, 0 errors

infra/sigs/rydberg_miner.py

@@ -8,16 +8,23 @@ Phase 3: Energy storage/translation materials - capacitance breakdown scaling.
 
 import json
 import os
+import time
 import urllib.request
 import urllib.parse
 from pathlib import Path
 
-TWO_ALPHA = 2 / 137
-RYDBERG_CM = 109677.581
-RYDBERG_MHZ = 109677.581 * 29.9792458  # Convert cm^-1 to MHz (R_H in frequency units)
-META_SOLID_RATIO = 1 / 7
+# Rate limiting for CORE API
+MAX_REQUESTS = 1000
+_request_count = 0
+_last_request_time = 0.0
 
 def query_core_api(query: str, limit: int = 5) -> list:
+    global _request_count, _last_request_time
+    
+    if _request_count >= MAX_REQUESTS:
+        print("CORE API request limit reached")
+        return []
+    
     api_key = os.getenv("CORE_API_KEY", "")
     if not api_key:
         key_file = Path.home() / ".core" / "api_key.txt"
@@ -25,20 +32,35 @@ def query_core_api(query: str, limit: int = 5) -> list:
             api_key = key_file.read_text().strip()
     if not api_key:
         return []
+    
     url = "https://api.core.ac.uk/v3/search/works"
     params = {"q": query, "limit": limit}
+    
+    # Exponential backoff based on rate limit
+    backoff = min(1.0 + (_request_count / 100), 10.0)
+    elapsed = time.time() - _last_request_time
+    if elapsed < backoff:
+        time.sleep(backoff - elapsed)
+    
     req = urllib.request.Request(
         f"{url}?{urllib.parse.urlencode(params)}",
         headers={"Authorization": f"Bearer {api_key}"}
     )
     try:
         with urllib.request.urlopen(req, timeout=10) as resp:
+            _request_count += 1
+            _last_request_time = time.time()
             data = json.loads(resp.read().decode())
             return [{"title": i.get("title", ""), "abstract": i.get("abstract", "")[:500] if i.get("abstract") else "", "year": i.get("publicationYear", ""), "doi": i.get("doi", "")} for i in data.get("results", [])]
     except Exception as e:
         print(f"CORE query error: {e}")
         return []
 
+TWO_ALPHA = 2 / 137
+RYDBERG_CM = 109677.581
+RYDBERG_MHZ = 109677.581 * 29.9792458  # Convert cm^-1 to MHz (R_H in frequency units)
+META_SOLID_RATIO = 1 / 7
+
 # Phase 1: Rydberg quantum defect data
 # F-state quantum defects for alkalis (literature values):
 # Rb F5/2: δ ≈ 3.9 (Li et al. Phys Rev A 67, 052502 2003)