feat(cargo-mono): colorize human output and improve publish failure excerpts (#306)

## Summary
- add global `--color <auto|always|never>` for cargo-mono human output
- add `CARGO_MONO_OUTPUT_COLOR` support and resolve precedence as:
`--color` > env > `NO_COLOR` > auto
- colorize human summary output across `list`, `changed`, `bump`, and
`publish` while keeping JSON output unchanged
- improve publish failure `details_excerpt` selection to prioritize
actionable lines (`error:` -> `failed to ...` -> first non-empty)
- update cargo-mono docs/contracts for color controls and output
invariants

## Validation
- `cargo fmt --all`
- `cargo test`

Author: kdy1

crates/cargo-mono/src/cli.rs

@@ -5,7 +5,7 @@ use std::{
 
 use clap::{ArgAction, Args, Parser, Subcommand};
 
-use crate::types::{BumpLevel, OutputFormat};
+use crate::types::{BumpLevel, OutputColorMode, OutputFormat};
 
 #[derive(Debug, Parser)]
 #[command(
@@ -18,6 +18,9 @@ pub struct Cli {
     /// Output format for command results.
     #[arg(long, global = true, value_enum, default_value_t = OutputFormat::Human)]
     pub output: OutputFormat,
+    /// Color mode for human output.
+    #[arg(long, global = true, value_enum)]
+    pub color: Option<OutputColorMode>,
 
     #[command(subcommand)]
     pub command: Command,

crates/cargo-mono/src/commands/bump.rs

@@ -6,10 +6,10 @@ use tracing::info;
 
 use crate::{
     cli::BumpArgs,
-    commands::{print_output, targeting},
+    commands::{print_output, targeting, OutputSettings},
     errors::Result,
     git,
-    types::{BumpLevel, OutputFormat},
+    types::BumpLevel,
     versioning, CargoMonoApp,
 };
 
@@ -73,7 +73,7 @@ struct BumpResult {
     tags: Vec<String>,
 }
 
-pub fn execute(args: &BumpArgs, output: OutputFormat, app: &CargoMonoApp) -> Result<i32> {
+pub fn execute(args: &BumpArgs, output: OutputSettings, app: &CargoMonoApp) -> Result<i32> {
     if args.level != BumpLevel::Prerelease && args.preid.is_some() {
         info!(
             command_path = "cargo-mono.bump",

crates/cargo-mono/src/commands/changed.rs

@@ -2,8 +2,10 @@ use serde::Serialize;
 use tracing::info;
 
 use crate::{
-    cli::ChangedArgs, commands::print_output, errors::Result, git, types::OutputFormat,
-    CargoMonoApp,
+    cli::ChangedArgs,
+    commands::{print_output, OutputSettings},
+    errors::Result,
+    git, CargoMonoApp,
 };
 
 #[derive(Debug, Serialize)]
@@ -17,7 +19,7 @@ struct ChangedResult {
     packages: Vec<String>,
 }
 
-pub fn execute(args: &ChangedArgs, output: OutputFormat, app: &CargoMonoApp) -> Result<i32> {
+pub fn execute(args: &ChangedArgs, output: OutputSettings, app: &CargoMonoApp) -> Result<i32> {
     let changed_files = git::changed_files(&args.base, args.include_uncommitted)?;
     let changed_packages = app
         .workspace

crates/cargo-mono/src/commands/list.rs

@@ -1,7 +1,11 @@
 use serde::Serialize;
 use tracing::info;
 
-use crate::{commands::print_output, errors::Result, types::OutputFormat, CargoMonoApp};
+use crate::{
+    commands::{print_output, OutputSettings},
+    errors::Result,
+    CargoMonoApp,
+};
 
 #[derive(Debug, Serialize)]
 struct ListPackage {
@@ -17,7 +21,7 @@ struct ListResult {
     packages: Vec<ListPackage>,
 }
 
-pub fn execute(output: OutputFormat, app: &CargoMonoApp) -> Result<i32> {
+pub fn execute(output: OutputSettings, app: &CargoMonoApp) -> Result<i32> {
     let packages = app
         .workspace
         .packages()