feat(kevin-exec): size from target_dollars, propagate price, bracket entries

Kevin signals never placed orders: the executor sized only from
sentiment_context["current_price"] (None for Kevin) so qty=0, and orders
were always built SIMPLE (stop/take pcts ignored).

- TradeSignal gains `current_price`; the bridge now sets it on publish
- risk_manager honors `target_dollars` directly (no strength re-scale) and
  resolves price from current_price then sentiment_context
- executor builds BRACKET orders for LONG entries carrying stop/take pcts;
  EXIT/SELL signals stay SIMPLE (the bridge sets pcts even on exits)

[ci skip]

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/services/kevin_signal_bridge/test_main.py

@@ -118,6 +118,65 @@ async def test_bridge_kill_switch_on_publishes_to_stream():
     cursor.advance.assert_awaited_with(1)
 
 
+async def test_bridge_attaches_current_price_to_signal():
+    """The bridge must propagate broker.get_latest_price onto the published
+    TradeSignal so the executor can size the position."""
+    config = MagicMock(
+        kevin_enable_trading=True,
+        kevin_stop_loss_pct=0.08,
+        kevin_take_profit_pct=0.20,
+        kevin_avoid_blocks_days=7,
+    )
+    cursor = AsyncMock()
+    cursor.last_seen_id.return_value = 0
+    publisher = AsyncMock()
+    publisher.publish.return_value = "1234-0"
+    aggregator = AsyncMock()
+    aggregator.fetch_pending.return_value = [
+        MagicMock(
+            id=1,
+            symbol="NVDA",
+            action=MagicMock(value="buy"),
+            conviction=Decimal("0.8"),
+            effective_conviction=Decimal("0.8"),
+            time_horizon=MagicMock(value="weeks"),
+        ),
+    ]
+    strategy = AsyncMock()
+    from shared.schemas.kevin import KevinDecisionType
+    strategy.evaluate_mention.return_value = MagicMock(
+        decision=KevinDecisionType.OPEN_LONG,
+        symbol="NVDA",
+        target_dollars=Decimal("3000"),
+        holding_days=10,
+        effective_conviction=Decimal("0.8"),
+        rationale="ok",
+    )
+    audit_writer = AsyncMock()
+    broker = AsyncMock()
+    broker.is_asset_tradable.return_value = True
+    broker.get_latest_price.return_value = Decimal("123.45")
+    broker.get_account.return_value = MagicMock(
+        equity=Decimal("100000"), cash=Decimal("100000")
+    )
+    broker.get_positions.return_value = []
+
+    bridge = KevinBridge(
+        config=config,
+        cursor=cursor,
+        publisher=publisher,
+        aggregator=aggregator,
+        strategy=strategy,
+        audit_writer=audit_writer,
+        broker=broker,
+    )
+    await bridge.process_one_pass()
+
+    publisher.publish.assert_awaited_once()
+    published_signal = publisher.publish.call_args[0][0]
+    assert published_signal.current_price == Decimal("123.45")
+
+
 async def test_bridge_advances_cursor_only_after_publish():
     """Race-condition guard: cursor must NOT advance if publish raises."""
     config = MagicMock(