bug(cli): raven tui reports node too low when a newer node exists later on PATH #198

Summary

raven tui fails with "Node version too low (found 20.20.1, need >= 22)" on
machines that DO have a recent Node installed (e.g. Homebrew node 26), while
raven agent works fine.

Root cause

find_node() in raven/cli/tui_commands.py has two defects:

1. No minimum-version filtering: it returned the first candidate whose
   --version parsed, ignoring _MIN_NODE_VERSION. The caller then rejected
   it if < 22 without asking for the next candidate, so a too-old node in an
   earlier priority tier shadowed a valid newer one.
2. PATH was probed via shutil.which("node"), which returns only the first
   hit. A stale < 22 node earlier on PATH (an old /usr/local/bin/node, an
   nvm/asdf shim, etc.) hid a newer node later on PATH.

raven agent needs no Node, so it was unaffected, which made this look like a
TUI/streaming problem.

Expected

find_node() returns the first node >= 22 across all PATH entries, in
priority order (RAVEN_NODE -> venv -> PATH -> private runtime); when nothing
qualifies it still reports the real version instead of "not found".

Environment

• OS: macOS
• Node on PATH: an older 20.x earlier, a 26.x later