Refine Starship prompt context and read-only indicators

[jiminu]

Summary

Make prompt context easier to identify while keeping the existing right-prompt order.

• Label runtime versions as node:24, java:21, and py:3.13(myenv), using Starship's native Python module and parent directory names for generic virtualenv names.
• Show a bold red [ro] after non-writable directories, and separate the username/hostname group from the following module without introducing spaces inside user@host.
• Disable Kubernetes by default; retain its detection settings and include the namespace when enabled. Document the resulting prompt behavior.

Validation

• Starship 1.26.0 rendering checks with temporary HOME: Python project detection, virtualenv activation/deactivation and generic names, missing Python, Node/Java labels, Kubernetes hidden by default, AWS profile display, local/SSH username spacing, and the read-only indicator including ANSI bold/red styling.
• git diff --check passed.
• Read-only code review found no actionable issues.
• An earlier bash scripts/check.sh run failed only in the existing test_mise_cleanup_preserves_current_and_project_versions_not_rollback_only; the same failure was reproduced on unchanged bd6809e. The final diff contains only configuration and documentation, so focused rendering checks were used per AGENTS.md. GitHub CI results are reported separately.
• GitHub CI passed: Linux/macOS shell checks, Ubuntu container installation E2E, macOS configuration lifecycle E2E, and pinned Neovim E2E. GitGuardian also passed.