Uncap watershed detail in the Node binding + sync docs

`6f163fc` widened watershed_detail from u8 to u32 in the core, CLI, and
Python binding but not the Node/wasm binding, which still assigned a u8 to
config.watershed_detail — a wasm build error (E0308). Widen the Node
Options field to u32 and refresh every "0..=255" watershed doc (CLI help,
Config field, .pyi, index.d.ts, and all three READMEs) to reflect that the
level is now uncapped (default 128; higher = more regions).

crates/vtracer-cli/src/main.rs

@@ -120,7 +120,7 @@ struct Args {
     #[arg(long)]
     adaptive_t: Option<f64>,
 
-    /// Watershed clustering: hierarchy cut level (0..=255, higher = more regions).
+    /// Watershed clustering: hierarchy cut level (default 128; higher = more regions, uncapped).
     #[arg(long, value_parser = clap::value_parser!(u32))]
     watershed_detail: Option<u32>,
 }