Pi v0.73.1 readies npm rename, login flows

This is the kind of release that matters more than it looks: less flashy capability, more fewer-footguns. For a CLI agent, update paths, auth flows, and terminal correctness are product quality, not housekeeping.

• –`pi update --self` now follows the package rename from `@mariozechner/pi-coding-agent` to `@earendil-works/pi-coding-agent`, which avoids breaking global installs during the namespace migration.
• –`/login` can now show multiple OAuth choices, making provider-specific auth flows workable instead of forcing a single brittle path.
• –`models.json` accepting comments and trailing commas is a real ergonomics win for local configuration, especially as model/provider setups get more complex.
• –The YAML frontmatter prompt fix removes a nasty CLI ambiguity that could misread user input as flags.
• –The TUI and inline-image fixes suggest the team is actively hardening the terminal UX, which is exactly where agents like this either feel reliable or feel flaky.