Add pair_signals per-pair producer registry

Ported from feature/eurusd-support: PAIR_PRODUCERS registry with
make_config() factories per pair. xauusd.make_config is a pure
PlatformConfig-defaults wrapper (equality with the inline construction
is enforced by test); eurusd.make_config carries the donor branch's
regime weights and gates as a pre-realism baseline.

Adds 4 registry tests. 154/154 pass.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

test_all.py

@@ -1761,7 +1761,60 @@ def _():
     assert r1.market_regime == r2.market_regime
 
 
-print("\n═══ Module 9: Engine Bug Fix Regressions ═══")
+print("\n═══ Module 9: pair_signals registry ═══")
+
+@test("pair_signals registry includes XAU/USD and EUR/USD")
+def _():
+    import pair_signals
+    pairs = pair_signals.get_supported_pairs()
+    assert XAUUSD in pairs, f"XAU missing from registry: {pairs}"
+    assert "EUR/USD" in pairs, f"EUR missing from registry: {pairs}"
+
+
+@test("xauusd.make_config equals inline PlatformConfig construction")
+def _():
+    import dataclasses
+    from pair_signals import PAIR_PRODUCERS
+    for tf, ctfs in [
+        (Timeframe.M5, [Timeframe.M15, Timeframe.H1]),
+        (Timeframe.M15, [Timeframe.M5, Timeframe.H1]),
+        (Timeframe.H1, [Timeframe.M15, Timeframe.H4]),
+    ]:
+        factory_cfg = PAIR_PRODUCERS[XAUUSD](tf, ctfs)
+        inline_cfg = PlatformConfig(
+            symbol=XAUUSD,
+            display_name="XAU/USD",
+            pip_value=0.10,
+            primary_timeframe=tf,
+            confirmation_timeframes=ctfs,
+        )
+        assert dataclasses.asdict(factory_cfg) == dataclasses.asdict(inline_cfg), \
+            f"XAU factory config differs from inline construction for {tf}"
+
+
+@test("eurusd.make_config produces EUR config with XAU strategy disabled")
+def _():
+    from pair_signals import PAIR_PRODUCERS
+    cfg = PAIR_PRODUCERS["EUR/USD"](Timeframe.M5, None)
+    assert cfg.symbol == "EUR/USD"
+    assert cfg.pip_value == 0.0001
+    assert cfg.xau_strategy.enabled is False
+    assert cfg.eur_strategy.enabled is True
+    assert cfg.technical.regime_weights_override, "EUR regime weights not applied"
+    assert cfg.confirmation_timeframes == [Timeframe.M15, Timeframe.H1]
+
+
+@test("produce_signal raises for unregistered pair")
+def _():
+    from pair_signals import produce_signal
+    try:
+        produce_signal("GBP/JPY", Timeframe.H1, None)
+        assert False, "Expected ValueError for unregistered pair"
+    except ValueError as e:
+        assert "GBP/JPY" in str(e)
+
+
+print("\n═══ Module 9b: Engine Bug Fix Regressions ═══")
 
 # ── 9a. Swing point NaN fix ──────────────────────────────────────────