Tighten signal pipeline: yfinance-only XAU/XAG, leaner Telegram /scan

- XAU/XAG always route to Yahoo Finance and skip Twelve Data entirely
  (excluded from batch prefetch, served per-symbol via yfinance).
- Daily chart cleanly skipped for gold/silver — engine drops it from MTF.
- Telegram /scan limited to EURUSD, USDJPY, GBPUSD, XAUUSD.
- SCAN_TIMEFRAMES reduced to single H1 primary; engine still pulls
  M15+H1+D1 internally via confirmation TFs (halves API credits per scan).
- Default confirmation TFs swapped H4 -> D1 in config and main.py.
- mtf_agreement_threshold kept at 2-of-3.
- CLAUDE.md cleaned up — old XAUUSD/synthetic-data bug reports removed.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

data_provider.py

@@ -157,6 +157,24 @@ class ForexDataProvider:
             if cached is not None and not cached.empty:
                 return cached
 
+        # Symbols not on Twelve Data (gold, silver) always use yfinance.
+        # D1 is intentionally skipped for these — yfinance daily for futures
+        # is unreliable and the engine drops missing confirmation TFs cleanly.
+        if symbol in _YF_FALLBACK_MAP:
+            if timeframe == Timeframe.D1:
+                raise DataUnavailableError(
+                    f"Daily chart skipped for {symbol} — gold/silver use M15/H1 only."
+                )
+            yf_df = self._fetch_yfinance_fallback(symbol, timeframe)
+            if yf_df is None:
+                raise DataUnavailableError(
+                    f"Yahoo Finance unavailable for {symbol} ({timeframe.value})."
+                )
+            df = self._validate_and_clean(yf_df, symbol, timeframe)
+            self._cache[cache_key] = df
+            self._cache_timestamps[cache_key] = now
+            return df
+
         df = self._fetch_twelve_data(symbol, timeframe, lookback_days)
         df = self._validate_and_clean(df, symbol, timeframe)
 
@@ -181,6 +199,12 @@ class ForexDataProvider:
         if lookback_days is None:
             lookback_days = self.config.data_lookback_days
 
+        # XAU/XAG aren't on Twelve Data — exclude them from the batch call,
+        # they'll be fetched individually via yfinance on demand.
+        td_symbols = [s for s in symbols if s not in _YF_FALLBACK_MAP]
+        if not td_symbols:
+            return
+
         now = time.time()
         for tf in timeframes:
             ttl = self._cache_ttl(tf)
@@ -188,13 +212,13 @@ class ForexDataProvider:
                 f"{s}_{tf.value}" in self._cache_timestamps
                 and (now - self._cache_timestamps[f"{s}_{tf.value}"]) < ttl
                 and not self._cache.get(f"{s}_{tf.value}", pd.DataFrame()).empty
-                for s in symbols
+                for s in td_symbols
             )
             if cached:
-                logger.debug(f"Skipping prefetch for {tf.value} — all {len(symbols)} symbols cached (TTL {ttl}s)")
+                logger.debug(f"Skipping prefetch for {tf.value} — all {len(td_symbols)} symbols cached (TTL {ttl}s)")
                 continue
             try:
-                self._batch_fetch_timeframe(symbols, tf, lookback_days)
+                self._batch_fetch_timeframe(td_symbols, tf, lookback_days)
                 time.sleep(1.0)  # brief pause between TF requests
             except Exception as e:
                 logger.warning(f"Batch prefetch failed for {tf.value}: {e}")