Add terminal capability fallback for progress UI

[F0RLE]

Summary

This PR adds a plain-text fallback for the live progress UI when stderr is not a terminal or ANSI / VT sequences are not supported.

What changed

• detect whether stderr supports terminal ANSI output
• keep the existing two-line ANSI UI when supported
• fall back to a plain-text single-line progress output when ANSI is unavailable
• update roadmap status for cross-platform runtime hardening

Why

The progress renderer was writing raw ANSI escape sequences directly, which could render badly on older Windows terminals or redirected stderr. This keeps the fast UI where it works and makes fallback behavior predictable where it does not.

Validation

• cargo fmt
• cargo check
• cargo test