feat: driver-based timeline strip, regime signal metrics, drivers editor

- instruments.json: add keywords array to every driver across 20 instruments
  (Fed, BCE, BOJ, OPEC, CPI, AI, EIA, etc.) for event-to-driver matching
- instrument_service.py: add update_instrument_drivers() persisting changes to JSON
  and refreshing in-memory cache
- instruments.py: add PUT /api/instruments/{id}/drivers endpoint (DriverUpdate model)
- InstrumentDashboard:
  * RegimeCard: replace regime score bars with 6-metric signal grid
    (MA50/MA200 position, MA50 slope, MA200 slope, momentum 20j, dist MA200, ATR vol ratio)
    with colour-coded values and contextual sub-labels (Golden cross, Surextension, etc.)
  * EventTimelineStrip: rows now keyed by top-4 instrument drivers (by weight)
    instead of LT/MT/CT; events matched via case-insensitive keyword scan against
    title + description + category; fallback dashed line when no events match
  * DriversPanel: inline edit panel (toggle via Drivers button in header);
    edit label, weight, keywords (comma-separated) per driver; add/remove drivers;
    saves via PUT /api/instruments/{id}/drivers; optimistic local state update

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/routers/instruments.py

@@ -3,6 +3,7 @@ Instrument Dashboard Router.
 Exposes per-instrument snapshot (price, indicators, regime, trend, events) and AI narrative.
 """
 from fastapi import APIRouter, HTTPException, Query
+from pydantic import BaseModel
 from typing import List, Dict, Any, Optional
 
 from services.instrument_service import (
@@ -10,8 +11,12 @@ from services.instrument_service import (
     get_instrument,
     get_snapshot,
     get_narrative,
+    update_instrument_drivers,
 )
 
+class DriverUpdate(BaseModel):
+    drivers: List[Dict[str, Any]]
+
 router = APIRouter(prefix="/api/instruments", tags=["instruments"])
 
 
@@ -63,3 +68,20 @@ async def generate_narrative(
         "instrument_name": config.get("name", instrument_id),
         "narrative": narrative,
     }
+
+
+@router.put("/{instrument_id}/drivers")
+def update_drivers(instrument_id: str, body: DriverUpdate) -> Dict[str, Any]:
+    """
+    Persist updated drivers (label, weight, keywords) for an instrument to instruments.json.
+    """
+    config = get_instrument(instrument_id)
+    if not config:
+        raise HTTPException(status_code=404, detail=f"Instrument '{instrument_id}' not found")
+
+    try:
+        update_instrument_drivers(instrument_id, body.drivers)
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=str(e))
+
+    return {"ok": True, "instrument_id": instrument_id.upper(), "drivers_count": len(body.drivers)}