fix(windows): make bubbletea TTY compile-safe

[coderbants]

Fixes #6

Overview

Keep the existing Unix TTY behavior intact while making the terminal lifecycle compile-safe on Windows. Unix raw-mode setup and restoration remain POSIX-gated; Windows exposes deterministic no-op fallbacks until a native console adapter is implemented. The optimized-movement probe also keeps its Unix-only file-descriptor dependency behind cfg.

Verification

• Native Windows cargo +nightly test --all-targets --no-fail-fast: passing in the isolated owner dependency-family recovery harness.
• Focused Bubbletea tests: passing, including the Windows terminal-boundary regression tests.
• cargo +nightly fmt: passing.
• git diff --check: passing.
• UPSTREAM_MAPPING.md documents the platform boundary and exact implementation/test targets.

Recovery context

This is the owner remediation for the Bonobo Windows release-dependency gate in Automaton coordination Issue #444. The branch was generated from the current protected Parent dev recovery envelope and is ready for independent review.