Hide the spline fine-tuning flags from CLI help

--corner-threshold, --segment-length, and --splice-threshold are still
accepted but no longer listed, and their -c/-l/-s short forms are gone:
the defaults serve virtually every conversion, and --simplify supersedes
them as the knob that actually moves output size (sweeping segment
length 3.5..=10 shifts the sample photo by 25% alone but under 2% once
simplify is on). README options block synced with the new help text.

CHANGELOG.md

@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Changed
 
 * `color_mode` is replaced by `clustering` (`color-cluster` | `bw` | `watershed`) across the CLI (`--clustering`), Rust (`Config::clustering`, enum `Clustering`), Python, and Node — the field selects the region-forming algorithm, not a color space.
+* The spline fine-tuning flags `--corner-threshold`, `--segment-length`, and `--splice-threshold` are hidden from CLI help (still accepted) and their short forms `-c`/`-l`/`-s` are removed — the defaults serve virtually every conversion, and `--simplify` supersedes them as the knob that actually moves output size.
 
 ### Fixed
 

README.md

@@ -86,9 +86,6 @@ Options:
   -f, --filter-speckle <FILTER_SPECKLE>      Discard patches smaller than X px in size (0..=128)
   -p, --color-precision <COLOR_PRECISION>    Significant bits per RGB channel (1..=8)
   -g, --gradient-step <GRADIENT_STEP>        Color difference between gradient layers (0..=255)
-  -c, --corner-threshold <CORNER_THRESHOLD>  Minimum momentary angle (degrees) to be a corner (0..=180)
-  -l, --segment-length <SEGMENT_LENGTH>      Subdivide until all segments are shorter than this (3.5..=10)
-  -s, --splice-threshold <SPLICE_THRESHOLD>  Minimum angle displacement (degrees) to splice a spline (0..=180)
       --simplify <TOLERANCE>                 Simplify curves: fewest cubics within this tolerance in px (try 1–2.5)
       --path-precision <PATH_PRECISION>      Decimal places to use in path coordinates
       --palette <PALETTE>                    Fixed palette: comma-separated hex colors, e.g. '#112233,#445566'
@@ -104,6 +101,12 @@ Options:
   -V, --version                              Print version
 ```
 
+The spline fine-tuning flags `--corner-threshold <0..=180>`,
+`--segment-length <3.5..=10>`, and `--splice-threshold <0..=180>` are still
+accepted but hidden from `--help`: their defaults (60 / 4 / 45) serve
+virtually every conversion, and `--simplify` is the knob that actually moves
+output size and smoothness.
+
 ### New in 1.0
 
 - **Positional arguments** — `vtracer in.png out.svg`.

crates/vtracer-cli/src/main.rs

@@ -60,19 +60,27 @@ struct Args {
     gradient_step: Option<i64>,
 
     /// Minimum momentary angle (degrees) to be a corner (0..=180).
-    #[arg(short = 'c', long, value_parser = clap::value_parser!(i64).range(0..=180))]
+    ///
+    /// Hidden from help: a fine-tuning knob few conversions need — the
+    /// default (60) serves; `--simplify` is the knob worth reaching for.
+    #[arg(long, hide = true, value_parser = clap::value_parser!(i64).range(0..=180))]
     corner_threshold: Option<i64>,
 
     /// Subdivide until all segments are shorter than this length (3.5..=10).
-    #[arg(short = 'l', long, value_parser = parse_segment_length)]
+    ///
+    /// Hidden from help: with `--simplify` reducing anchors by an explicit
+    /// error tolerance, this legacy knob's effect on output is negligible.
+    #[arg(long, hide = true, value_parser = parse_segment_length)]
     segment_length: Option<f64>,
 
     /// Minimum angle displacement (degrees) to splice a spline (0..=180).
-    #[arg(short = 's', long, value_parser = clap::value_parser!(i64).range(0..=180))]
+    ///
+    /// Hidden from help: a fine-tuning knob few conversions need — the
+    /// default (45) serves; `--simplify` is the knob worth reaching for.
+    #[arg(long, hide = true, value_parser = clap::value_parser!(i64).range(0..=180))]
     splice_threshold: Option<i64>,
 
-    /// Simplify curves (spline mode): re-fit with the fewest cubics staying
+    /// Simplify curves: fewest cubics within this tolerance in px (try 1-2.5).
-    /// within this tolerance in px (try 1–2.5; paper.js uses 2.5).
     #[arg(long, value_name = "TOLERANCE", value_parser = parse_simplify_tolerance)]
     simplify: Option<f64>,