feat(console): add structured error handling, verbosity, and suggestions

Implement Phase 7.2 error handling & UX infrastructure:

- Add exit_code module with MozartError, bail()/bail_silent() helpers,
  and Composer-compatible exit code constants (0-5, 100)
- Redesign Console struct with Verbosity enum (Quiet/Normal/Verbose/
  VeryVerbose/Debug), ANSI auto-detection via IsTerminal, and
  verbosity-gated output methods (info/verbose/debug/error)
- Thread Console through all 33 command execute() signatures
- Replace all std::process::exit() calls with structured MozartError
  returns handled in main()
- Migrate eprintln\! status messages to console.info() for quiet-mode
  suppression
- Add suggest module with Levenshtein distance and "Did you mean?"
  formatting for future package name suggestions

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

1 files changed, 19 insertions, 2 deletions

diff --git a/crates/mozart/src/main.rs b/crates/mozart/src/main.rs
index cd85137..dd85279 100644
--- a/crates/mozart/src/main.rs
+++ b/crates/mozart/src/main.rs
@@ -1,7 +1,24 @@
 use clap::Parser;
 use mozart::commands;
+use mozart::exit_code;
 
-fn main() -> anyhow::Result<()> {
+fn main() {
     let cli = commands::Cli::parse();
-    commands::execute(&cli)
+    match commands::execute(&cli) {
+        Ok(()) => {}
+        Err(e) => {
+            // Check if this is a structured MozartError with a specific exit code.
+            if let Some(mozart_err) = e.downcast_ref::<exit_code::MozartError>() {
+                // Only print a message when there is one (bail_silent produces empty message).
+                if !mozart_err.message.is_empty() {
+                    eprintln!("{}", mozart::console::error(&mozart_err.message));
+                }
+                std::process::exit(mozart_err.exit_code);
+            }
+
+            // Generic anyhow error — print and exit with GENERAL_ERROR.
+            eprintln!("{}", mozart::console::error(&format!("{e:#}")));
+            std::process::exit(exit_code::GENERAL_ERROR);
+        }
+    }
 }