Extract CLI command router

[chubes4]

Summary

• Extract CLI argv command and subcommand dispatch into packages/cli/src/command-router.ts.
• Keep command parsing, output formatting, runtime execution, and public command behavior in place while index.ts now wires handlers through runCli(argv).
• Move JSPI respawn handling with the router because it depends on the selected top-level command.

Tests

• npm run build
• npm run command-registry-smoke
• npm run discovery-command-smoke
• npm run workspace-policy-smoke
• npm run recipe-dry-run-smoke
• npm run wp-codebox -- commands --json
• npm run wp-codebox -- schema recipe --json
• npm run wp-codebox -- help

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (openai/gpt-5.5)
• Used for: Drafted the focused CLI router extraction, ran build/smoke verification, and prepared the PR summary for Chris to review.