fix: make e2e test_node resilient to transient git clone failures

[bigcat88]

The test_node e2e test flakes intermittently on all platforms (Ubuntu, macOS, Windows) because git clone of comfyui-animatediff-evolved fails with exit code 128 due to GitHub rate-limiting on Actions runners.

Two problems made this worse than it needed to be.
First, comfy node install returns exit code 0 even when git clone fails internally (ComfyUI-Manager's cm-cli.py swallows the exception). The test passed the returncode check and then failed with a confusing "node not in list" assertion.
Second, a single transient network error caused the whole test to fail with no retry.

This adds --exit-on-fail to the install command so the CLI properly reports failure, and wraps the install in a retry loop (3 attempts) to handle transient network errors.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

@@           Coverage Diff           @@
##             main     #381   +/-   ##
=======================================
  Coverage   63.44%   63.44%           
=======================================
  Files          33       33           
  Lines        3699     3699           
=======================================
  Hits         2347     2347           
  Misses       1352     1352           

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