fix: enlarge every sub-2px stroker width to 2px, per Daniel's ruling

Knob track arc, inner-dial needle, and mini velocity-trace all sat below the analytic stroker's opaque-core floor. Raised to 2px; updated visual-design-language.md and core/ui/CLAUDE.md to match; kept the 1px-behavior test, corrected its stale comment.

src/shell/instrument/editor_internal.h

@@ -113,11 +113,14 @@ inline void drawTitleBand(LICE_IBitmap* bmp, const instrument::ui::Rect& title,
 }
 
 // Stroke widths for the radial faces. Every arc is ONE analytic stroke (editor_stroke.h) whose
-// outer edge sits on the knob's radius, so the centerline is inset by half the width.
-inline constexpr float kKnobTrackArcPx = 1.0f;
+// outer edge sits on the knob's radius, so the centerline is inset by half the width. Every
+// width here is >= 2 px, the stroker's guaranteed-opaque-core floor (core/ui/CLAUDE.md) —
+// anything narrower modulates peak alpha with pixel-grid alignment instead of pinning solid.
+inline constexpr float kKnobTrackArcPx = 2.0f;
 inline constexpr float kKnobValueArcPx = 3.0f;
 inline constexpr float kInnerDialArcPx = 2.0f;
 inline constexpr float kKnobNeedlePx = 2.0f;
+inline constexpr float kInnerDialNeedlePx = 2.0f;
 
 // Draws one radial knob face: param_slider owns the value<->angle map; this turns it into
 // LICE calls. LICE takes radians, and drawing the 7->5 o'clock sweep through the top needs
@@ -198,7 +201,7 @@ inline void drawInnerDial(LICE_IBitmap* bmp, const instrument::ui::Rect& innerRe
                 toLice(ui::roleColor(arcRole)));
     const KnobPoint tip = instrument::ui::knobNeedlePoint(kg, arc, v);
     strokeLineAA(bmp, static_cast<float>(kg.centerX), static_cast<float>(kg.centerY),
-                 static_cast<float>(tip.x), static_cast<float>(tip.y), 1.0f,
+                 static_cast<float>(tip.x), static_cast<float>(tip.y), kInnerDialNeedlePx,
                  toLice(ui::roleColor(disabled ? ui::Role::TextDim : ui::Role::AccentTertiary)));
 }