fix(cli): pick the first node >= 22 across all PATH entries

[arelchan]

Change description

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

Two bugs in find_node() (raven/cli/tui_commands.py):

1. No minimum-version filtering. It returned the first candidate whose --version merely parsed, regardless of _MIN_NODE_VERSION. The caller then rejected it if < 22 without ever asking for the next candidate -- so a too-old node in an earlier priority tier shadowed a valid newer one.
2. PATH probed with 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.

Together: a user with node 26 on PATH but a 20.x earlier on PATH got "node too low". raven agent was unaffected (no Node needed), which made it look like a TUI/streaming problem.

Fix

• Enumerate every node on PATH (not just the first).
• Return the first candidate that meets _MIN_NODE_VERSION, in priority order (RAVEN_NODE -> venv -> PATH -> private runtime).
• Keep the highest below-minimum candidate so, when nothing qualifies, the caller still reports the real version (found 20.20.1, need >= 22) instead of a bare "not found".

Tests

Added to tests/test_cli_tui_bootstrap.py:

• test_find_node_skips_below_min_and_scans_all_path -- a 20.20.1 earlier on PATH + a 26.5.0 later => find_node returns 26.5.0.
• test_find_node_reports_below_min_when_nothing_qualifies -- only a 20.20.1 => returns it (so the caller can show the version).

Type of change

• Bug fix
• New feature
• Document
• Others

Checklists

Development

• Lint rules pass locally (ruff check / ruff format)
• Application changes have been tested thoroughly
• Automated tests covering modified code pass

Code review

• Pull request has a descriptive title and context useful to a reviewer

Note (unrelated, pre-existing)

test_find_node_discovers_windows_private_runtime fails on non-Windows hosts on main already (its mock sets sys.platform="win32" but find_node's Priority-4 branch keys off os.name == "nt"). It is not run by CI's make test-python subset, so CI stays green. Left untouched here to keep this PR scoped; flagging it for a separate fix.