fix: address rate limit detection false positives and reset-time cap

- Narrow `\boverloaded\b` regex to require server/api/system context,
  preventing false positives when Claude discusses method/operator
  overloading in OOP code (C++, Java, C#, etc.)
- Restore 24-hour cap for absolute reset-time delays instead of 1-hour
  clamp, avoiding unnecessary retry loops when rate limits reset hours
  in the future
- Add test for Retry-After: 0 returning 0 (regression lock for the
  `is not None` fix)
- Add false positive tests for "overloaded" in programming context

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

rate_limit_utils.py

@@ -18,7 +18,7 @@ RATE_LIMIT_REGEX_PATTERNS = [
     r"\bstatus\s*429\b",          # "status 429", "status429"
     r"\berror\s*429\b",           # "error 429", "error429"
     r"\b429\s+too\s+many",        # "429 too many"
-    r"\boverloaded\b",            # "overloaded"
+    r"\b(?:server|api|system)\s+(?:is\s+)?overloaded\b",  # "server is overloaded", "api overloaded"
     r"\bquota\s*exceeded\b",      # "quota exceeded"
 ]