- dep_ensure.py: use get_hermes_home() instead of hand-rolled env var
- dep_ensure.py: add "chrome" to browser name list (was inconsistent with browser_tool.py)
- main.py _cmd_update_check: use detect_install_method() directly instead of redundant .git check
- main.py _cmd_update_pip: build command list directly instead of fragile split() on display string
- banner.py: rename _check_via_pypi → check_via_pypi (cross-module public API)
Before: missing node → hard exit; missing browser → FileNotFoundError.
After: both try ensure_dependency() first, which prompts interactively
and delegates installation to install.sh --ensure.
ripgrep and ffmpeg already degrade gracefully (grep fallback, skip
conversion) so they don't need wiring.
Also documents the design rationale in dep_ensure.py: detection and
prompting live in Python (portable, instant, UX-integrated); only
the actual installation delegates to install.sh (1900 lines of
battle-tested OS/package-manager logic).