is_valid_version() previously only matched strict 3-part semver (X.Y.Z),
causing a false ERROR log on startup whenever requirements.txt contained a
2-part constraint such as SQLAlchemy>=2.0.
Steps to reproduce (before fix):
ComfyUI currently logs at ERROR level on every startup:
[2026-04-21 16:06:11.527] Invalid version format in requirements.txt: 2.0
The offending entry is SQLAlchemy>=2.0 (merged in #13316).
Root cause:
The regex r'^(\d+)\.(\d+)\.(\d+)$' requires exactly three numeric parts.
PEP 440 treats 2.0 and 2.0.0 as equivalent release identifiers, so the
constraint is valid but the validator rejected it.
Fix:
Replace the regex with r'^\d+(\.\d+)*$' which accepts 1-, 2-, and 3-part
(and longer) all-numeric release identifiers: 2, 2.0, 2.0.0, 1.25.3.
Also downgrade the log level from ERROR to WARNING, since an unparseable
entry is skipped gracefully and does not break the install.
Previously issue #12813 was worked around by changing simpleeval>=1.0 to
simpleeval>=1.0.0 in requirements.txt. This commit fixes the underlying
parser so the same workaround is not needed for future entries.
