Add commit-echo config command to view current configuration

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Task summary

Add a commit-echo config command that displays the current configuration (provider, model, endpoint, history size) with the API key masked (e.g., sk-••••••••).

Why this is a good first issue

This task is self-contained, requires adding only one new command file, and follows the same pattern as the existing init, suggest, and history commands. It touches no core logic—just CLI wiring and reading the config file.

Suggested files or areas

• src/commands/config.ts — new command implementation
• src/index.ts — register the new command in the CLI program
• src/config/store.ts — loadConfig is already available

Acceptance criteria

• Running commit-echo config prints the current provider, model, endpoint, history size, and API key (masked)
• Running commit-echo config when no config exists shows a helpful message suggesting commit-echo init
• The command follows the same pattern (intro/outro from @clack/prompts) as other commands
• npm run build succeeds with no errors

Extra context

• See src/commands/history.ts for a minimal example of reading and displaying config data
• The Config interface is defined in src/types.ts
• API key masking: display only the first 2–4 characters followed by ••••