Fix: point install's next step at the agent chat, not the terminal (#472) (#532)

The install completion message said to run /impeccable init "in your AI
harness", and users pasted it into their shell instead (bash: /impeccable:
No such file or directory). Say the command is typed in the AI coding
agent's chat, and give `npx impeccable init` a pointed redirect instead of
the generic unknown-command error. A real path named `init` still routes
to detect as before.

Prepared with AI assistance (Cursor agent), directed by @abdulwahabone.

Co-authored-by: Cursor <cursoragent@cursor.com>

cli/bin/cli.js

@@ -77,6 +77,12 @@ Compatibility:
     process.argv = [process.argv[0], process.argv[1], ...args];
     const { detectCli } = await import('../engine/detect-antipatterns.mjs');
     await detectCli();
+  } else if (command === 'init') {
+    // The follow-up mistake from issue #472: `/impeccable init` belongs in an AI
+    // coding agent's chat, and a user who typed it into their shell is likely to
+    // retry it here as `npx impeccable init`.
+    console.error(`"init" is not a CLI command. Type /impeccable init in your AI coding agent's chat (Claude Code, Cursor, Codex, ...), not in this terminal.`);
+    process.exit(1);
   } else {
     // An unknown bareword: a mistyped command (or an old cached version run
     // against newer docs). Fail loudly instead of silently statting it as a path.