feat(cockpit): dependency-free inline-SVG nav sparkline

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/fxhnt/adapters/web/charts.py

@@ -0,0 +1,23 @@
+"""Dependency-free inline-SVG charts. Server-rendered so the cockpit needs no JS charting library — the SVG
+string is embedded directly in the HTML. nav_sparkline maps a NAV series to a polyline scaled to the box."""
+from __future__ import annotations
+
+
+def nav_sparkline(nav: list[float], *, width: int = 120, height: int = 28,
+                  color: str = "#3fb950") -> str:
+    box = f'<svg width="{width}" height="{height}" viewBox="0 0 {width} {height}" '\
+          'xmlns="http://www.w3.org/2000/svg">'
+    if not nav:
+        return box + "</svg>"
+    lo, hi = min(nav), max(nav)
+    span = (hi - lo) or 1.0
+    n = len(nav)
+    step = width / (n - 1) if n > 1 else 0.0
+    pts = []
+    for i, v in enumerate(nav):
+        x = i * step
+        y = height - (v - lo) / span * (height - 2) - 1     # 1px padding, y inverted
+        pts.append(f"{x:.1f},{y:.1f}")
+    stroke = color if nav[-1] >= nav[0] else "#f85149"
+    return (box + f'<polyline fill="none" stroke="{stroke}" stroke-width="1.5" '
+            f'points="{" ".join(pts)}" /></svg>')

tests/unit/test_charts.py

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+"""nav_sparkline renders a self-contained inline SVG polyline from a NAV series (no JS, no external libs)."""
+from __future__ import annotations
+
+from fxhnt.adapters.web.charts import nav_sparkline
+
+
+def test_sparkline_is_svg_with_points() -> None:
+    svg = nav_sparkline([1.0, 1.01, 1.005, 1.02], width=100, height=20)
+    assert svg.startswith("<svg") and svg.rstrip().endswith("</svg>")
+    assert "<polyline" in svg and "points=" in svg
+
+
+def test_sparkline_empty_series_is_safe() -> None:
+    svg = nav_sparkline([], width=100, height=20)
+    assert svg.startswith("<svg") and "polyline" not in svg
+
+
+def test_sparkline_flat_series_does_not_divide_by_zero() -> None:
+    svg = nav_sparkline([1.0, 1.0, 1.0], width=100, height=20)
+    assert "<polyline" in svg            # flat line, no exception