Add error handling for Claude Code imperative settings

## Overview
The imperative Claude Code settings in `utils/install-claude-code.sh` currently suppress errors with `2>/dev/null` but don't handle failures or provide feedback.

## Current State
```bash
claude config set -g autoUpdate true 2>/dev/null
claude config set -g preferredNotifChannel terminal_bell 2>/dev/null
claude config set -g verbose true 2>/dev/null
```

## Problem
- Silent failures if Claude Code isn't properly authenticated
- No feedback if settings fail to apply
- User won't know if configuration was successful

## Proposed Solution
Add minimal error handling that:
1. Captures the exit code of each command
2. Provides user feedback on failures
3. Continues with remaining settings even if one fails
4. Returns appropriate exit code

## Considerations
- Keep it minimal per PR readability contract
- Avoid colorful logging bloat
- Focus on actionable feedback

Related: #1025, #1026

Read utils/install-claude-code.sh and inspect the three claude config set commands that currently redirect errors to /dev/null. Run the installer to observe the existing behavior; done means failures produce actionable feedback, later settings still run, and the script returns an appropriate exit code.

Written by the indexing model from the issue text.