fix(indicator): use common::Ticks for GaugeAxis to allow disabling ticks

gauge.axis.ticks accepts "outside", "inside", or "" (disabled). TicksDirection
only covers inside/outside, so "no ticks" was inexpressible. Switch to
common::Ticks (Outside/Inside/None -> "outside"/"inside"/"") and add a test that
Ticks::None serializes to "".

Addresses roborev review job 3599 (the tickmode finding in that review was a
false positive: the v3.7.0 schema lists gauge.axis.tickmode as
["auto","linear","array"], so TickMode::Auto is valid).

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

Author: jqnatividad

plotly/src/traces/indicator.rs

@@ -6,10 +6,10 @@ use plotly_derive::FieldSetter;
 use serde::Serialize;
 
 use crate::color::Color;
-use crate::layout::{ArrayShow, TicksDirection};
+use crate::layout::ArrayShow;
 use crate::private::{NumOrString, NumOrStringCollection};
 use crate::{
-    common::{Domain, ExponentFormat, Font, Line, PlotType, TickFormatStop, TickMode},
+    common::{Domain, ExponentFormat, Font, Line, PlotType, TickFormatStop, TickMode, Ticks},
     Trace,
 };
 
@@ -185,8 +185,9 @@ pub struct GaugeAxis {
     /// [`TickMode::Array`]).
     #[serde(rename = "ticktext")]
     tick_text: Option<Vec<String>>,
-    /// Determines whether ticks are drawn inside or outside the axis line.
-    ticks: Option<TicksDirection>,
+    /// Determines whether ticks are drawn inside or outside the axis line
+    /// ([`Ticks::None`] disables them).
+    ticks: Option<Ticks>,
     /// Sets the tick length (in px).
     #[serde(rename = "ticklen")]
     tick_length: Option<usize>,
@@ -587,7 +588,7 @@ mod tests {
                 "mid".to_string(),
                 "high".to_string(),
             ])
-            .ticks(TicksDirection::Outside)
+            .ticks(Ticks::Outside)
             .tick_length(8)
             .tick_width(2)
             .tick_color("gray")
@@ -651,6 +652,13 @@ mod tests {
         assert!(v["tickformatstops"].is_array());
     }
 
+    #[test]
+    fn serialize_gauge_axis_ticks_none() {
+        // The gauge-axis schema allows "" to disable tick marks.
+        let axis = GaugeAxis::new().ticks(Ticks::None);
+        assert_eq!(to_value(axis).unwrap()["ticks"], json!(""));
+    }
+
     #[test]
     fn serialize_indicator_legend_and_uirevision() {
         let trace = Indicator::new(1.0)