Respect `NO_COLOR` and always show the command as a header when paging `uv help` output (#16908)

## Summary

Fix #16879 and address an additional issue where the pager prompt would
be bold regardless of NO_COLOR.

<img width="1437" height="483" alt="image"
src="https://github.com/user-attachments/assets/7234129a-364b-40c6-834a-57ac34212925"
/>

## Test Plan

Ran the test suite and manually verified against `less` 679 and `busybox` v1.34.1.

Checked with and without `NO_COLOR` on both "normal" `less`, `busybox` `less`, and `more`.

crates/uv/src/commands/help.rs

@@ -6,7 +6,7 @@ use std::{fmt::Display, fmt::Write};
 use anstream::{ColorChoice, stream::IsTerminal};
 use anyhow::{Result, anyhow};
 use clap::CommandFactory;
-use itertools::{Either, Itertools};
+use itertools::Itertools;
 use owo_colors::OwoColorize;
 use which::which;
 
@@ -70,9 +70,9 @@ pub(crate) fn help(query: &[String], printer: Printer, no_pager: bool) -> Result
         .render_long_help()
     };
 
-    let help_ansi = match anstream::Stdout::choice(&std::io::stdout()) {
+    let want_color = match anstream::Stdout::choice(&std::io::stdout()) {
-        ColorChoice::Always | ColorChoice::AlwaysAnsi => Either::Left(help.ansi()),
+        ColorChoice::Always | ColorChoice::AlwaysAnsi => true,
-        ColorChoice::Never => Either::Right(help.clone()),
+        ColorChoice::Never => false,
         // We just asked anstream for a choice, that can't be auto
         ColorChoice::Auto => unreachable!(),
     };
@@ -80,22 +80,19 @@ pub(crate) fn help(query: &[String], printer: Printer, no_pager: bool) -> Result
     let is_terminal = std::io::stdout().is_terminal();
     let should_page = !no_pager && !is_root && is_terminal;
 
-    if should_page {
+    if should_page && let Some(pager) = Pager::try_from_env() {
-        if let Some(pager) = Pager::try_from_env() {
+        let query = query.join(" ");
-            let content = if pager.supports_colors() {
+        if want_color && pager.supports_colors() {
-                help_ansi
+            pager.spawn(format!("{}: {query}", "uv help".bold()), help.ansi())?;
-            } else {
-                Either::Right(help.clone())
-            };
-            pager.spawn(
-                format!("{}: {}", "uv help".bold(), query.join(" ")),
-                &content,
-            )?;
         } else {
-            writeln!(printer.stdout(), "{help_ansi}")?;
+            pager.spawn(format!("uv help: {query}"), help)?;
         }
     } else {
-        writeln!(printer.stdout(), "{help_ansi}")?;
+        if want_color {
+            writeln!(printer.stdout(), "{}", help.ansi())?;
+        } else {
+            writeln!(printer.stdout(), "{help}")?;
+        }
     }
 
     Ok(ExitStatus::Success)
@@ -131,9 +128,9 @@ struct Pager {
 }
 
 impl PagerKind {
-    fn default_args(&self, prompt: String) -> Vec<String> {
+    fn default_args(&self) -> Vec<String> {
         match self {
-            Self::Less => vec!["-R".to_string(), "-P".to_string(), prompt],
+            Self::Less => vec!["-R".to_string()],
             Self::More => vec![],
             Self::Other(_) => vec![],
         }
@@ -183,7 +180,7 @@ impl FromStr for Pager {
 
 impl Pager {
     /// Display `contents` using the pager.
-    fn spawn(self, prompt: String, contents: impl Display) -> Result<()> {
+    fn spawn(self, heading: String, contents: impl Display) -> Result<()> {
         use std::io::Write;
 
         let command = self
@@ -193,7 +190,7 @@ impl Pager {
             .unwrap_or(OsString::from(self.kind.to_string()));
 
         let args = if self.args.is_empty() {
-            self.kind.default_args(prompt)
+            self.kind.default_args()
         } else {
             self.args
         };
@@ -209,7 +206,10 @@ impl Pager {
             .ok_or_else(|| anyhow!("Failed to take child process stdin"))?;
 
         let contents = contents.to_string();
-        let writer = std::thread::spawn(move || stdin.write_all(contents.as_bytes()));
+        let writer = std::thread::spawn(move || {
+            let _ = write!(stdin, "{heading}\n\n");
+            let _ = stdin.write_all(contents.as_bytes());
+        });
 
         drop(child.wait());
         drop(writer.join());