[cli] Project templates: enterprise-search, code-mode #76

Depends on: Issues #62 & #64 (enterprise-search), Issue #66 (code-mode)

Summary

Python already ships python-starter, python-pizzaz and python-oauth, the last mapping to nitrostack/templates/flight-booking; these match the TypeScript starter, pizzaz and oauth templates. Missing: enterprise-search ("BM25 progressive tool discovery") and code-mode ("QuickJS WebAssembly sandboxing").

Reference

• ts:../cli/templates/typescript-enterprise-search,
• typescript-code-mode;
• OFFICIAL_TEMPLATES in nitrostack/cli/main.py.

Scope

• Each template ships pyproject.toml, .python-version, uv.toml, requirements.txt and a README, like the existing templates.
• Register both in OFFICIAL_TEMPLATES and the template prompt.

Acceptance criteria

• nitrostack-py init demo --template <name> --skip-install </dev/null produces a project that passes nitrostack-py validate.
• upgrade and pack work on it.